Chediak-Higashi syndrome (CHS) is characterized by partial oculocutaneous albinism, immunodeficiency, and a mild bleeding tendency. Approximately 85% of affected individuals develop the accelerated phase, or hemophagocytic lymphohistiocytosis, a life-threatening, hyperinflammatory condition. All affected individuals including adolescents and adults with atypical CHS and children with classic CHS who have successfully undergone allogenic hematopoietic stem cell transplantation (HSCT) develop neurologic findings during early adulthood.

Mycosis fungoides is a malignant T-cell lymphoma of the skin, first reported (and named) by Alibert (1835). Sezary syndrome is a leukemic variant of mycosis fungoides defined by erythroderma with greater than 80% of the skin showing redness, adenopathy and greater than 1,000 circulating Sezary cells/microliter with a CD4+CD26- or CD4+CD7- phenotype. Sezary cells have a type 2 helper T cell cytokine profile. Sezary syndrome has a median overall survival time of only 2.4 years in patients with Sezary cells at a density of greater than 10,000 cells/microliter or 5.4 years in patients with 1,000-10,000 Sezary cells/microliter. Mycosis fungoides and Sezary syndrome are the most common cutaneous T-cell lymphomas. Sezary syndrome can arise de novo or can appear following years of chronic mycosis fungoides. Both are thought to arise from clonal expansion of CD4+ helper T cells responding to chronic antigen stimulation (summary by Wang et al., 2015).

A greater than normal number of blood cells in the reticuloendothelial system.

The phenotype of acid sphingomyelinase deficiency (ASMD) occurs along a continuum. Individuals with the severe early-onset form, infantile neurovisceral ASMD, were historically diagnosed with Niemann-Pick disease type A (NPD-A). The later-onset, chronic visceral form of ASMD is also referred to as Niemann-Pick disease type B (NPD-B). A phenotype with intermediate severity is also known as chronic neurovisceral ASMD (NPD-A/B). The most common presenting symptom in NPD-A is hepatosplenomegaly, usually detectable by age three months; over time the liver and spleen become massive in size. Psychomotor development progresses no further than the 12-month level, after which neurologic deterioration is relentless. Failure to thrive typically becomes evident by the second year of life. A classic cherry-red spot of the macula of the retina, which may not be present in the first few months, is eventually present in all affected children. Interstitial lung disease caused by storage of sphingomyelin in pulmonary macrophages results in frequent respiratory infections and often respiratory failure. Most children succumb before the third year of life. NPD-B generally presents later than NPD-A, and the manifestations are less severe. NPD-B is characterized by progressive hepatosplenomegaly, gradual deterioration in liver and pulmonary function, osteopenia, and atherogenic lipid profile. No central nervous system (CNS) manifestations occur. Individuals with NPD-A/B have symptoms that are intermediate between NPD-A and NPD-B. The presentation in individuals with NPD-A/B varies greatly, although all are characterized by the presence of some CNS manifestations. Survival to adulthood can occur in individuals with NPD-B and NPD-A/B.

Periodic fever, immunodeficiency, and thrombocytopenia syndrome (PFITS) is an autosomal recessive immunologic disorder with variable manifestations. Common features include early-onset recurrent respiratory infections, stomatitis, and cutaneous infections. Organisms usually include bacteria such as pneumococcus, Staphylococcus, and H. influenzae, but severe viral infections, including varicella, may also occur. Laboratory investigations may show neutropenia, neutrophilia, leukocytosis, or lymphopenia, although levels of immune cells may also be normal. Detailed studies often show impaired neutrophil chemotaxis associated with increased or abnormal F-actin levels, and impaired, normal, or even increased oxidative burst, depending on the stimulus. B- and T-cell abnormalities have also been observed. Some patients develop autoimmune manifestations, including chronic thrombocytopenia, anemia, and periodic fevers, associated with activation of the inflammasome. Early death may occur; however, hematopoietic stem cell transplantation may be curative (summary by Kuhns et al., 2016, Standing et al., 2017, and Pfajfer et al., 2018).

IPEX (immune dysregulation, polyendocrinopathy, enteropathy, X-linked) syndrome is characterized by systemic autoimmunity, typically beginning in the first year of life. Presentation is most commonly the clinical triad of watery diarrhea, endocrinopathy (most commonly insulin-dependent diabetes mellitus), and eczematous dermatitis. Most children have other autoimmune phenomena including cytopenias, autoimmune hepatitis, or nephropathy; lymphadenopathy, splenomegaly, alopecia, arthritis, and lung disease related to immune dysregulation have all been observed. Fetal presentation of IPEX includes hydrops, echogenic bowel, skin desquamation, IUGR, and fetal akinesia. Without aggressive immunosuppression or bone marrow transplantation, the majority of affected males die within the first one to two years of life from metabolic derangements, severe malabsorption, or sepsis; a few with a milder phenotype have survived into the second or third decade of life.

Mevalonate kinase deficiency is a condition characterized by recurrent episodes of fever, which typically begin during infancy. Each episode of fever lasts about 3 to 6 days, and the frequency of the episodes varies among affected individuals. In childhood the fevers seem to be more frequent, occurring as often as 25 times a year, but as the individual gets older the episodes occur less often.\n\nMevalonate kinase deficiency has additional signs and symptoms, and the severity depends on the type of the condition. There are two types of mevalonate kinase deficiency: a less severe type called hyperimmunoglobulinemia D syndrome (HIDS) and a more severe type called mevalonic aciduria (MVA).\n\nDuring episodes of fever, people with HIDS typically have enlargement of the lymph nodes (lymphadenopathy), abdominal pain, joint pain, diarrhea, skin rashes, and headache. Occasionally they will have painful sores called aphthous ulcers around their mouth. In females, these may also occur around the vagina. Rarely, people with HIDS develop a buildup of protein deposits (amyloidosis) in the kidneys that can lead to kidney failure. Fever episodes in individuals with HIDS can be triggered by vaccinations, surgery, injury, or stress. Most people with HIDS have abnormally high levels of immune system proteins called immunoglobulin D (IgD) and immunoglobulin A (IgA) in the blood. It is unclear why some people with HIDS have high levels of IgD and IgA and some do not. Elevated levels of these immunoglobulins do not appear to cause any signs or symptoms. Individuals with HIDS do not have any signs and symptoms of the condition between fever episodes and typically have a normal life expectancy.\n\nPeople with MVA have signs and symptoms of the condition at all times, not just during episodes of fever. Affected children have developmental delay, problems with movement and balance (ataxia), recurrent seizures (epilepsy), progressive problems with vision, and failure to gain weight and grow at the expected rate (failure to thrive). Individuals with MVA typically have an unusually small, elongated head. In childhood or adolescence, affected individuals may develop eye problems such as inflammation of the eye (uveitis), a blue tint in the white part of the eye (blue sclera), an eye disorder called retinitis pigmentosa that causes vision loss, or clouding of the lens of the eye (cataracts). Affected adults may have short stature and may develop muscle weakness (myopathy) later in life. During fever episodes, people with MVA may have an enlarged liver and spleen (hepatosplenomegaly), lymphadenopathy, abdominal pain, diarrhea, and skin rashes. Children with MVA who are severely affected with multiple problems may live only into early childhood; mildly affected individuals may have a normal life expectancy.

Chronic infantile neurologic cutaneous and articular syndrome (CINCA) is an early-onset, severe, chronic inflammatory disease, characterized by cutaneous symptoms, central nervous system involvement, and arthropathy (Feldmann et al., 2002). See also familial cold autoinflammatory syndrome-1 (FCAS1, CAPS1; 120100), an allelic disorder with a less severe phenotype.

Hyper-IgM syndrome type 2 (HIGM2) is a rare immunodeficiency characterized by normal or elevated serum IgM levels with absence of IgG, IgA, and IgE, resulting in a profound susceptibility to bacterial infections. For a discussion of genetic heterogeneity of immunodeficiency with hyper-IgM, see HIGM1 (308230).

Hyper-IgM syndrome is a condition characterized by normal or increased serum IgM concentrations associated with low or absent serum IgG, IgA, and IgE concentrations, indicating a defect in the class-switch recombination (CSR) process. For a discussion of genetic heterogeneity of immunodeficiency with hyper-IgM, see HIGM1 (308230).

Heme oxygenase-1 deficiency (HMOX1D) is a rare autosomal recessive disorder with a complex clinical presentation including direct antibody negative hemolytic anemia, low bilirubin, and hyperinflammation (summary by Chau et al., 2020). Other features may include asplenia and nephritis (Radhakrishnan et al., 2011).

Spondyloenchondrodysplasia with immune dysregulation (SPENCDI) is an immunoosseous dysplasia combining the typical metaphyseal and vertebral bone lesions of spondyloenchondrodysplasia (SPENCD) with immune dysfunction and neurologic involvement. The skeletal dysplasia is characterized by radiolucent and irregular spondylar and metaphyseal lesions that represent islands of chondroid tissue within bone. The vertebral bodies show dorsally accentuated platyspondyly with disturbance of ossification. Clinical abnormalities such as short stature, rhizomelic micromelia, increased lumbar lordosis, barrel chest, facial anomalies, and clumsy movements may be present (Menger et al., 1989). Central nervous system involvement includes spasticity, mental retardation, and cerebral calcifications, and immune dysregulation ranges from autoimmunity to immunodeficiency. Neurologic and autoimmune manifestations have been observed in different combinations within a single family, suggesting that this disorder may be defined by specific radiographic features but has remarkably pleiotropic manifestations (Renella et al., 2006). Briggs et al. (2016) also noted variability in skeletal, neurologic, and immune phenotypes, which was sometimes marked between members of the same family. Classification of the Enchondromatoses In their classification of the enchondromatoses, Spranger et al. (1978) called Ollier disease and Maffucci syndrome types I and II enchondromatosis, respectively; metachondromatosis (156250), type III; and spondyloenchondrodysplasia (SPENCD), also called spondyloenchondromatosis, type IV; enchondromatosis with irregular vertebral lesions, type V; and generalized enchondromatosis, type VI. Halal and Azouz (1991) added 3 tentative categories to the 6 in the classification of Spranger et al. (1978). Pansuriya et al. (2010) suggested a new classification of enchondromatosis (multiple enchondromas).

Chronic granulomatous disease (CGD) is a primary immunodeficiency disorder of phagocytes (neutrophils, monocytes, macrophages, and eosinophils) resulting from impaired killing of bacteria and fungi. CGD is characterized by severe recurrent bacterial and fungal infections and dysregulated inflammatory responses resulting in granuloma formation and other inflammatory disorders such as colitis. Infections typically involve the lung (pneumonia), lymph nodes (lymphadenitis), liver (abscess), bone (osteomyelitis), and skin (abscesses or cellulitis). Granulomas typically involve the genitourinary system (bladder) and gastrointestinal tract (often the pylorus initially, and later the esophagus, jejunum, ileum, cecum, rectum, and perirectal area). Some males with X-linked CGD have McLeod neuroacanthocytosis syndrome as the result of a contiguous gene deletion. While CGD may present anytime from infancy to late adulthood, the vast majority of affected individuals are diagnosed before age five years. Use of antimicrobial prophylaxis and therapy has greatly improved overall survival.

Roifman syndrome is a multisystem disorder characterized by growth retardation, spondyloepiphyseal dysplasia, retinal dystrophy, distinctive facial dysmorphism, and immunodeficiency (summary by de Vries et al., 2006).

Caspase 8 deficiency is a syndrome of lymphadenopathy and splenomegaly, marginal elevation of 'double-negative T cells' (DNT; T-cell receptor alpha/beta+, CD4-/CD8-), defective FAS-induced apoptosis, and defective T-, B-, and natural killer (NK)-cell activation, with recurrent bacterial and viral infections (summary by Madkaikar et al., 2011).

Immunodeficiency-41 is an autosomal recessive complex disorder of immune dysregulation. Affected individuals present in infancy with recurrent viral, fungal, and bacterial infections, lymphadenopathy, and variable autoimmune features, such as autoimmune enteropathy and eczematous skin lesions. Immunologic studies show a defect in T-cell regulation (summary by Goudy et al., 2013).

Chronic granulomatous disease (CGD) is a primary immunodeficiency disorder of phagocytes (neutrophils, monocytes, macrophages, and eosinophils) resulting from impaired killing of bacteria and fungi. CGD is characterized by severe recurrent bacterial and fungal infections and dysregulated inflammatory responses resulting in granuloma formation and other inflammatory disorders such as colitis. Infections typically involve the lung (pneumonia), lymph nodes (lymphadenitis), liver (abscess), bone (osteomyelitis), and skin (abscesses or cellulitis). Granulomas typically involve the genitourinary system (bladder) and gastrointestinal tract (often the pylorus initially, and later the esophagus, jejunum, ileum, cecum, rectum, and perirectal area). Some males with X-linked CGD have McLeod neuroacanthocytosis syndrome as the result of a contiguous gene deletion. While CGD may present anytime from infancy to late adulthood, the vast majority of affected individuals are diagnosed before age five years. Use of antimicrobial prophylaxis and therapy has greatly improved overall survival.

Chronic granulomatous disease (CGD) is a primary immunodeficiency disorder of phagocytes (neutrophils, monocytes, macrophages, and eosinophils) resulting from impaired killing of bacteria and fungi. CGD is characterized by severe recurrent bacterial and fungal infections and dysregulated inflammatory responses resulting in granuloma formation and other inflammatory disorders such as colitis. Infections typically involve the lung (pneumonia), lymph nodes (lymphadenitis), liver (abscess), bone (osteomyelitis), and skin (abscesses or cellulitis). Granulomas typically involve the genitourinary system (bladder) and gastrointestinal tract (often the pylorus initially, and later the esophagus, jejunum, ileum, cecum, rectum, and perirectal area). Some males with X-linked CGD have McLeod neuroacanthocytosis syndrome as the result of a contiguous gene deletion. While CGD may present anytime from infancy to late adulthood, the vast majority of affected individuals are diagnosed before age five years. Use of antimicrobial prophylaxis and therapy has greatly improved overall survival.

Chronic granulomatous disease (CGD) is a primary immunodeficiency disorder of phagocytes (neutrophils, monocytes, macrophages, and eosinophils) resulting from impaired killing of bacteria and fungi. CGD is characterized by severe recurrent bacterial and fungal infections and dysregulated inflammatory responses resulting in granuloma formation and other inflammatory disorders such as colitis. Infections typically involve the lung (pneumonia), lymph nodes (lymphadenitis), liver (abscess), bone (osteomyelitis), and skin (abscesses or cellulitis). Granulomas typically involve the genitourinary system (bladder) and gastrointestinal tract (often the pylorus initially, and later the esophagus, jejunum, ileum, cecum, rectum, and perirectal area). Some males with X-linked CGD have McLeod neuroacanthocytosis syndrome as the result of a contiguous gene deletion. While CGD may present anytime from infancy to late adulthood, the vast majority of affected individuals are diagnosed before age five years. Use of antimicrobial prophylaxis and therapy has greatly improved overall survival.

Autoimmune lymphoproliferative syndrome (ALPS), caused by defective lymphocyte homeostasis, is characterized by the following: Non-malignant lymphoproliferation (lymphadenopathy, hepatosplenomegaly with or without hypersplenism) that often improves with age. Autoimmune disease, mostly directed toward blood cells. Lifelong increased risk for both Hodgkin and non-Hodgkin lymphoma. In ALPS-FAS (the most common and best-characterized type of ALPS, associated with heterozygous germline pathogenic variants in FAS), non-malignant lymphoproliferation typically manifests in the first years of life, inexplicably waxes and wanes, and then often decreases without treatment in the second decade of life; in many affected individuals, however, neither splenomegaly nor the overall expansion of lymphocyte subsets in peripheral blood decreases. Although autoimmunity is often not present at the time of diagnosis or at the time of the most extensive lymphoproliferation, autoantibodies can be detected before autoimmune disease manifests clinically. In ALPS-FAS caused by homozygous or compound heterozygous (biallelic) pathogenic variants in FAS, severe lymphoproliferation occurs before, at, or shortly after birth, and usually results in death at an early age. ALPS-sFAS, resulting from somatic FAS pathogenic variants in selected cell populations, notably the alpha/beta double-negative T cells (a/ß-DNT cells), appears to be similar to ALPS-FAS resulting from heterozygous germline pathogenic variants in FAS, although lower incidence of splenectomy and lower lymphocyte counts have been reported in ALPS-sFAS and no cases of lymphoma have yet been published.

A rare genetic primary immunodeficiency with characteristics of increased susceptibility to fungal infections that typically manifest as recurrent, chronic mucocutaneous candidiasis, systemic candidiasis with meningoencephalitis and deep dermatophytosis. Dermatophytes invade skin, hair, nails, lymph nodes and brain, resulting in erythematosquamous lesions, nodular subcutaneous or ulcerative infiltrations, severe onychomycosis and lymphadenopathy.

Familial hemophagocytic lymphohistiocytosis-2 (FHL2) is an autosomal recessive disorder of immune dysregulation with onset in infancy or early childhood. It is characterized clinically by fever, edema, hepatosplenomegaly, and liver dysfunction. Neurologic impairment, seizures, and ataxia are frequent. Laboratory studies show pancytopenia, coagulation abnormalities, hypofibrinogenemia, and hypertriglyceridemia. There is increased production of cytokines, such as gamma-interferon (IFNG; 147570) and TNF-alpha (191160), by hyperactivation and proliferation of T cells and macrophages. Activity of cytotoxic T cells and NK cells is reduced, consistent with a defect in cellular cytotoxicity. Bone marrow, lymph nodes, spleen, and liver show features of hemophagocytosis. Chemotherapy and/or immunosuppressant therapy may result in symptomatic remission, but the disorder is fatal without bone marrow transplantation (summary by Dufourcq-Lagelouse et al., 1999, Stepp et al., 1999, and Molleran Lee et al., 2004). For a general phenotypic description and a discussion of genetic heterogeneity of FHL, see 267700.

Hemophagocytic lymphohistiocytosis is a hyperinflammatory disorder clinically diagnosed based on the fulfillment of 5 of 8 criteria, including fever, splenomegaly, bicytopenia, hypertriglyceridemia and/or hypofibrinogenemia, hemophagocytosis, low or absent natural killer (NK) cell activity, hyperferritinemia, and high soluble IL2 receptor levels (IL2R; 147730). The disorder typically presents in infancy or early childhood. Persistent remission is rarely achieved with chemo- or immunotherapy; hematopoietic stem cell transplantation is the only cure (summary by Muller et al., 2014). For a phenotypic description and a discussion of genetic heterogeneity of familial hemophagocytic lymphohistiocytosis (FHL), see 267700.

The histiocytosis-lymphadenopathy plus syndrome comprises features of 4 histiocytic disorders previously thought to be distinct: Faisalabad histiocytosis (FHC), sinus histiocytosis with massive lymphadenopathy (SHML), H syndrome, and pigmented hypertrichosis with insulin-dependent diabetes mellitus syndrome (PHID). FHC was described as an autosomal recessive disease involving joint deformities, sensorineural hearing loss, and subsequent development of generalized lymphadenopathy and swellings in the eyelids that contain histiocytes (summary by Morgan et al., 2010). SHML, or familial Rosai-Dorfman disease, was described as a rare cause of lymph node enlargement in children, consisting of chronic massive enlargement of cervical lymph nodes frequently accompanied by fever, leukocytosis, elevated erythrocyte sedimentation rate, and polyclonal hypergammaglobulinemia. Extranodal sites were involved in approximately 25% of patients, including salivary glands, orbit, eyelid, spleen, and testes. The involvement of retropharyngeal lymphoid tissue sometimes caused snoring and sleep apnea (summary by Kismet et al., 2005). H syndrome was characterized by cutaneous hyperpigmentation and hypertrichosis, hepatosplenomegaly, heart anomalies, and hypogonadism; hearing loss was also found in about half of patients, and many had short stature. PHID was characterized by predominantly antibody-negative insulin-dependent diabetes mellitus associated with pigmented hypertrichosis and variable occurrence of other features of H syndrome, with hepatosplenomegaly occurring in about half of patients (Cliffe et al., 2009). Bolze et al. (2012) noted that mutations in the SLC29A3 gene (612373) had been implicated in H syndrome, PHID, FHC, and SHML, and that some patients presented a combination of features from 2 or more of these syndromes, leading to the suggestion that these phenotypes should be grouped together as 'SLC29A3 disorder.' Bolze et al. (2012) suggested that the histologic features of the lesions seemed to be the most uniform phenotype in these patients. In addition, the immunophenotype of infiltrating cells in H syndrome patients was shown to be the same as that seen in patients with the familial form of Rosai-Dorfman disease, further supporting the relationship between these disorders (Avitan-Hersh et al., 2011; Colmenero et al., 2012).

Immunodeficiency-54 is an autosomal recessive primary immunodeficiency characterized by severe intra- and extrauterine growth retardation, microcephaly, decreased numbers of natural killer (NK) cells, and recurrent viral infections, most often affecting the respiratory tract and leading to respiratory failure. Affected individuals also have adrenal insufficiency requiring corticosteroid replacement therapy and may have an increased susceptibility to cancer. Laboratory studies of patient cells showed a DNA repair defect (summary by Gineau et al., 2012).

Mevalonic aciduria (MEVA), the first recognized defect in the biosynthesis of cholesterol and isoprenoids, is a consequence of a deficiency of mevalonate kinase (ATP:mevalonate 5-phosphotransferase; EC 2.7.1.36). Mevalonic acid accumulates because of failure of conversion to 5-phosphomevalonic acid, which is catalyzed by mevalonate kinase. Mevalonic acid is synthesized from 3-hydroxy-3-methylglutaryl-CoA, a reaction catalyzed by HMG-CoA reductase (142910). Mevalonic aciduria is characterized by dysmorphology, psychomotor retardation, progressive cerebellar ataxia, and recurrent febrile crises, usually manifesting in early infancy, accompanied by hepatosplenomegaly, lymphadenopathy, arthralgia, and skin rash. The febrile crises are similar to those observed in hyperimmunoglobulinemia D and to periodic fever syndrome (HIDS; 260920), which is also caused by mutation in the MVK gene (summary by Prietsch et al., 2003).

Familial cold autoinflammatory syndrome-2 (FCAS2) is an autosomal dominant autoinflammatory disorder characterized by episodic and recurrent rash, urticaria, arthralgia, myalgia, and headache. In most patients, these episodes are accompanied by fever and serologic evidence of inflammation. Most, but not all, patients report exposure to cold as a trigger for the episodes. Additional features may include abdominal pain, thoracic pain, and sensorineural deafness. The age at onset is variable, ranging from the first year of life to middle age, and the severity and clinical manifestations are heterogeneous (summary by Shen et al., 2017). For a phenotypic description and a discussion of genetic heterogeneity of familial cold autoinflammatory syndrome, see FCAS1 (120100).

Omenn syndrome is an autosomal recessive disorder characterized by severe combined immunodeficiency (SCID) associated with erythrodermia, hepatosplenomegaly, lymphadenopathy, and alopecia. B cells are mostly absent, T-cell counts are normal to elevated, and T cells are frequently activated and express a restricted T-cell receptor (TCR) repertoire (summary by Ege et al., 2005). Another distinct form of familial histiocytic reticulocytosis (267700) is caused by mutation in the perforin-1 gene (PRF1; 170280) on chromosome 10q22.

Immunodeficiency-10 (IMD10) is an autosomal recessive primary immunodeficiency characterized by onset of recurrent infections in childhood due to defective T- and NK-cell function, although the severity is variable. Affected individuals may also have hypotonia, hypohidrosis, or dental enamel hypoplasia consistent with amelogenesis imperfecta (summary by Parry et al., 2016).

Familial hemophagocytic lymphohistiocytosis-5 with or without microvillus inclusion disease (FHL5) is an autosomal recessive hyperinflammatory disorder characterized clinically by fever, hepatosplenomegaly, pancytopenia, coagulation abnormalities, and other laboratory findings. Some patients have neurologic symptoms due to inflammatory CNS disease. There is uncontrolled and ineffective proliferation and activation of T lymphocytes, NK cells, and macrophages that infiltrate multiple organs, including liver, spleen, lymph nodes, and the CNS. The phenotype is variable: some patients may present in early infancy with severe diarrhea, prior to the onset of typical FHL features, whereas others present later in childhood and have a more protracted course without diarrhea. The early-onset diarrhea is due to enteropathy reminiscent of microvillus inclusion disease (see MVID, 251850). The enteropathy, which often necessitates parenteral feeding, may be the most life-threatening issue even after hematopoietic stem cell transplantation (HSCT). More variable features include sensorineural hearing loss and hypogammaglobulinemia. Treatment with immunosuppressive drugs and chemotherapy can ameliorate signs and symptoms of FHL in some patients, but the only curative therapy for FHL is HSCT. HSCT is not curative for enteropathy associated with the disorder, despite hematologic and immunologic reconstitution (summary by Meeths et al., 2010; Pagel et al., 2012; Stepensky et al., 2013). For a phenotypic description and a discussion of genetic heterogeneity of familial hemophagocytic lymphohistiocytosis (FHL, HLH), see 267700.

Common variable immunodeficiency (CVID) is a clinically and genetically heterogeneous group of disorders characterized by antibody deficiency, hypogammaglobulinemia, recurrent bacterial infections, and an inability to mount an antibody response to antigen. The defect results from a failure of B-cell differentiation and impaired secretion of immunoglobulins; the numbers of circulating B cells are usually in the normal range, but can be low. Most individuals with CVID have onset of infections after age 10 years. CVID represents the most common form of primary immunodeficiency disorders and is the most common form of primary antibody deficiency. Approximately 10 to 20% of patients with a diagnosis of CVID have a family history of the disorder (reviews by Chapel et al., 2008, Conley et al., 2009, and Yong et al., 2009). Genetic Heterogeneity of Common Variable Immunodeficiency Common variable immunodeficiency is a genetically heterogeneous disorder. See also CVID2 (240500), caused by mutation in the TACI gene (TNFRSF13B; 604907); CVID3 (613493), caused by mutation in the CD19 gene (107265); CVID4 (613494), caused by mutation in the BAFFR gene (TNFRSF13C; 606269); CVID5 (613495), caused by mutation in the CD20 gene (112210); CVID6 (613496), caused by mutation in the CD81 gene (186845); CVID7 (614699), caused by mutation in the CD21 gene (CR2; 120650); CVID8 (614700), caused by mutation in the LRBA gene (606453); CVID10 (615577), caused by mutation in the NFKB2 gene (164012); CVID11 (615767), caused by mutation in the IL21 gene (605384); CVID12 (616576), caused by mutation in the NFKB1 gene (164011); CVID13 (616873), caused by mutation in the IKZF1 gene (603023); CVID14 (617765), caused by mutation in the IRF2BP2 gene (615332); and CVID15 (620670), caused by heterozygous mutation in the SEC61A1 gene (609213). The disorder formerly designated CVID9 has been found to be a form of autoimmune lymphoproliferative disorder; see ALPS3 (615559).

XMEN is an X-linked recessive immunodeficiency characterized by CD4 (186940) lymphopenia, severe chronic viral infections, and defective T-lymphocyte activation (Li et al., 2011). Affected individuals have chronic Epstein-Barr virus (EBV) infection and are susceptible to the development of EBV-associated B-cell lymphoproliferative disorders. Magnesium supplementation may be therapeutic (summary by Li et al., 2014).

IMD31C is a disorder of immunologic dysregulation with highly variable manifestations resulting from autosomal dominant gain-of-function mutations in STAT1 (600555). Most patients present in infancy or early childhood with chronic mucocutaneous candidiasis (CMC). Other highly variable features include recurrent bacterial, viral, fungal, and mycoplasmal infections, disseminated dimorphic fungal infections, enteropathy with villous atrophy, and autoimmune disorders, such as hypothyroidism or diabetes mellitus. A subset of patients show apparently nonimmunologic features, including osteopenia, delayed puberty, and intracranial aneurysms. Laboratory studies show increased activation of gamma-interferon (IFNG; 147570)-mediated inflammation (summary by Uzel et al., 2013 and Sampaio et al., 2013).

Lymphoproliferative syndrome-1 is an autosomal recessive primary immunodeficiency characterized by onset in early childhood of Epstein-Barr virus (EBV)-associated immune dysregulation, manifest as lymphoma, lymphomatoid granulomatosis, hemophagocytic lymphohistiocytosis, Hodgkin disease, and/or hypogammaglobulinemia. Autoimmune disorders, such as autoimmune hemolytic anemia or renal disease, may also occur. Patients show a high EBV viral load and decreased invariant natural killer T cells. It is unknown whether patients with ITK mutations are intrinsically susceptible to development of lymphoma or dysgammaglobulinemia in the absence of EBV infection (summary by Stepensky et al., 2011; Linka et al., 2012). For a discussion of genetic heterogeneity of lymphoproliferative syndrome, see XLP1 (308240).

Common variable immunodeficiency-8 with autoimmunity is an autosomal recessive disorder of immune dysregulation. Affected individuals have early childhood onset of recurrent infections, particularly respiratory infections, and also develop variable autoimmune disorders, including idiopathic thrombocytopenic purpura, autoimmune hemolytic anemia, and inflammatory bowel disease. The presentation and phenotype are highly variable, even within families (summary by Lopez-Herrera et al., 2012 and Alangari et al., 2012). Immunologic findings are also variable and may include decreased B cells, hypogammaglobulinemia, and deficiency of CD4+ T regulatory (Treg) cells (Charbonnier et al., 2015). For a general description and a discussion of genetic heterogeneity of common variable immunodeficiency, see CVID1 (607594).

Lymphoproliferative syndrome-2, also known as CD27 deficiency, is an autosomal recessive immunodeficiency disorder associated with persistent symptomatic EBV viremia, hypogammaglobulinemia, and impairment in specific antibody function resulting from impaired T cell-dependent B-cell responses and T-cell dysfunction (summary by van Montfrans et al., 2012). The phenotype can vary significantly, from asymptomatic borderline-low hypogammaglobulinemia, to a full-blown symptomatic systemic inflammatory response with life-threatening EBV-related complications, including hemophagocytic lymphohistiocytosis, a lymphoproliferative disorder, and malignant lymphoma requiring stem cell transplantation (summary by Salzer et al., 2013). For a discussion of genetic heterogeneity of lymphoproliferative syndrome, see XLP1 (308240).

Activated PI3K-delta syndrome (also known as APDS) is a disorder that impairs the immune system. Individuals with this condition often have low numbers of white blood cells (lymphopenia), particularly B cells and T cells. Normally, these cells recognize and attack foreign invaders, such as viruses and bacteria, to prevent infection. The severity of activated PI3K-delta syndrome varies widely. Some people may have multiple, severe infections while others show mild symptoms to none at all.\n\nMost commonly, people with activated PI3K-delta syndrome develop recurrent infections that begin in childhood, particularly in the lungs, sinuses, and ears. Over time, recurrent respiratory tract infections can lead to a condition called bronchiectasis, which damages the passages leading from the windpipe to the lungs (bronchi) and can cause breathing problems. People with activated PI3K-delta syndrome may also have chronic active viral infections, such as Epstein-Barr virus, herpes simplex virus, or cytomegalovirus infections.\n\nThere are two types of activated PI3K-delta syndrome, each with different genetic causes.\n\nAnother possible feature of activated PI3K-delta syndrome is abnormal clumping of white blood cells. These clumps can lead to enlarged lymph nodes (lymphadenopathy) or an enlarged spleen (splenomegaly). The white blood cells can also build up to form solid masses (nodular lymphoid hyperplasia), usually in the moist lining of the airways or intestines. While nodular lymphoid hyperplasia is not cancerous (benign), activated PI3K-delta syndrome increases the risk of developing forms of blood cancer called Hodgkin lymphoma and non-Hodgkin lymphoma.\n\nSome people with activated PI3K-delta syndrome develop autoimmunity, which occurs when the body attacks its own tissues and organs by mistake.

Autosomal dominant IRF8 deficiency, or IMD32A, causes an abnormal peripheral blood myeloid phenotype with a marked loss of CD11C (ITGAX; 151510)-positive/CD1C (188340)-positive dendritic cells, resulting in selective susceptibility to mycobacterial infections (Hambleton et al., 2011).

Immunodeficiency-7 (IMD7) is an autosomal recessive immunologic disorder characterized by onset of recurrent bacterial and viral infections in infancy or early childhood. Affected individuals may also have features of immune dysregulation, including lymphadenopathy and presence of autoantibodies. Laboratory studies show increased serum IgE, low numbers of T cells, low TCR-alpha/beta cells, and increased TCR-gamma/delta cells. The disorder often results in death in childhood, although bone marrow transplant is effective (summary by Morgan et al., 2011 and Rawat et al., 2021).

Autoimmune lymphoproliferative syndrome type III is an autosomal recessive disorder of immune dysregulation. The phenotype is variable, but most patients have significant lymphadenopathy associated with variable autoimmune manifestations. Some patients may have recurrent infections. Lymphocyte accumulation results from a combination of impaired apoptosis and excessive proliferation (summary by Oliveira, 2013). For a general description and a discussion of genetic heterogeneity of ALPS, see 601859.

Adenosine deaminase 2 deficiency (DADA2) is a complex systemic autoinflammatory disorder in which vasculopathy/vasculitis, dysregulated immune function, and/or hematologic abnormalities may predominate. Inflammatory features include intermittent fevers, rash (often livedo racemosa/reticularis), and musculoskeletal involvement (myalgia/arthralgia, arthritis, myositis). Vasculitis, which usually begins before age ten years, may manifest as early-onset ischemic (lacunar) and/or hemorrhagic strokes, or as cutaneous or systemic polyarteritis nodosa. Hypertension and hepatosplenomegaly are often found. More severe involvement may lead to progressive central neurologic deficits (dysarthria, ataxia, cranial nerve palsies, cognitive impairment) or to ischemic injury to the kidney, intestine, and/or digits. Dysregulation of immune function can lead to immunodeficiency or autoimmunity of varying severity; lymphadenopathy may be present and some affected individuals have had lymphoproliferative disease. Hematologic disorders may begin early in life or in late adulthood, and can include lymphopenia, neutropenia, pure red cell aplasia, thrombocytopenia, or pancytopenia. Of note, both interfamilial and intrafamilial phenotypic variability (e.g., in age of onset, frequency and severity of manifestations) can be observed; also, individuals with biallelic ADA2 pathogenic variants may remain asymptomatic until adulthood or may never develop clinical manifestations of DADA2.

Immunodeficiency-27A (IMD27A) results from autosomal recessive (AR) IFNGR1 deficiency. Patients with complete IFNGR1 deficiency have a severe clinical phenotype characterized by early and often fatal mycobacterial infections. The disorder can thus be categorized as a form of mendelian susceptibility to mycobacterial disease (MSMD). Bacillus Calmette-Guerin (BCG) and environmental mycobacteria are the most frequent pathogens, and infection typically begins before the age of 3 years. Plasma from patients with complete AR IFNGR1 deficiency usually contains large amounts of IFNG (147570), and their cells do not respond to IFNG in vitro. In contrast, cells from patients with partial AR IFNGR1 deficiency, which is caused by a specific mutation in IFNGR1, retain residual responses to high IFNG concentrations. Patients with partial AR IFNGR1 deficiency are susceptible to BCG and environmental mycobacteria, but they have a milder clinical disease and better prognosis than patients with complete AR IFNGR1 deficiency. The clinical features of children with complete AR IFNGR1 deficiency are usually more severe than those in individuals with AD IFNGR1 deficiency (IMD27B), and mycobacterial infection often occurs earlier (mean age of 1.3 years vs 13.4 years), with patients having shorter mean disease-free survival. Salmonellosis is present in about 5% of patients with AR or AD IFNGR1 deficiency, and other infections have been reported in single patients (review by Al-Muhsen and Casanova, 2008).

Polyglucosan body myopathy-1 (PGBM1) is an autosomal recessive disorder characterized by onset in childhood of progressive proximal muscle weakness, resulting in difficulties in ambulation. Most patients also develop progressive dilated cardiomyopathy, which may necessitate cardiac transplant in severe cases. A small subset of patients present with severe immunodeficiency and a hyperinflammatory state in very early childhood (summary by Boisson et al., 2012 and Nilsson et al., 2013). Genetic Heterogeneity of Polyglucosan Body Myopathy See also PGBM2 (616199), caused by mutation in the GYG1 gene (603942) on chromosome 3q24.

Immune dysregulation with autoimmunity, immunodeficiency, and lymphoproliferation (IDAIL) is an autosomal dominant complex immune disorder with highly variable presentation and clinical manifestations. Prominent features include recurrent infections often associated with hypogammaglobulinemia, autoimmune features such as autoimmune cytopenias, and abnormal lymphocytic infiltration of nonlymphoid organs, including the lungs, brain, and gastrointestinal tract, resulting in enteropathy. Laboratory studies often show lymphopenia and abnormal T and B cell subsets. The variable features are a result of impaired function of Treg cells, which play a role in immune homeostasis (summary by Kuehn et al., 2014; Schwab et al., 2018, and Lopez-Nevado et al., 2021). The disorder shows overlapping features with autoimmune lymphoproliferative syndrome (ALPS); for a general description and a discussion of genetic heterogeneity of ALPS, see 601859.

IMD38 predisposes individuals to severe clinical disease upon infection with weakly virulent mycobacteria, including Mycobacterium bovis Bacille Calmette-Guerin (BCG) vaccines (Bogunovic et al., 2012). Patients do not experience severe disease in response to viral infection. Affected individuals have intracranial calcification (Zhang et al., 2015).

Autoinflammation, panniculitis, and dermatosis syndrome (AIPDS) is an autosomal recessive autoinflammatory disease characterized by neonatal onset of recurrent fever, erythematous rash with painful nodules, painful joints, and lipodystrophy. Additional features may include diarrhea, increased serum C-reactive protein (CRP), leukocytosis, and neutrophilia in the absence of any infection. Patients exhibit no overt primary immunodeficiency (Damgaard et al., 2016 and Zhou et al., 2016).

IMD52 is an autosomal recessive primary immunodeficiency with variable manifestations, including severe combined immunodeficiency, hematologic autoimmune disorders, progressive lymphopenia and hypogammaglobulinemia, and lymphoproliferation with splenomegaly. Patients develop severe recurrent infections from infancy, and most die without bone marrow transplantation. The variable clinical features result from a defect in T-cell receptor signaling (summary by Keller et al., 2016 and Bacchelli et al., 2017).

DFNA34 is an autosomal dominant form of postlingual, slowly progressive sensorineural hearing loss with variable severity and variable additional features. Some patients have pure hearing loss without significant additional features, whereas some patients have features of an autoinflammatory disorder with systemic manifestations, including periodic fevers, arthralgias, and episodic urticaria. The disorder results from abnormally increased activation of the inflammatory pathway, and treatment with an IL1 receptor antagonist (see 147679) may be effective if started early (summary by Nakanishi et al., 2017).

Immunodeficiency-71 with inflammatory disease and congenital thrombocytopenia (IMD71) is an autosomal recessive immunologic disorder characterized by the onset of recurrent infections and inflammatory features such as vasculitis and eczema in infancy or early childhood. Infectious agents include bacteria and viruses. Laboratory findings are variable, but usually show thrombocytopenia, sometimes with abnormal platelet morphology, increased serum IgE, IgA, or IgM, leukocytosis, decreased or increased T lymphocytes, and increased eosinophils. Detailed studies show impaired neutrophil and T-cell chemotaxis, as well as impaired T-cell activation due to defects in F-actin (see 102610) polymerization (summary by Brigida et al., 2018).

Familial Hemophagocytic lymphohistiocytosis (FHL) is a rare primary immunodeficiency characterized by a macrophage activation syndrome with an onset usually occurring within a few months or less common several years after birth.

Proteasome-associated autoinflammatory syndrome-1 (PRAAS1) is an autosomal recessive disorder characterized by early childhood onset of annular erythematous plaques on the face and extremities with subsequent development of partial lipodystrophy and laboratory evidence of immune dysregulation. More variable features include recurrent fever, severe joint contractures, muscle weakness and atrophy, hepatosplenomegaly, basal ganglia calcifications, and microcytic anemia (summary by Agarwal et al., 2010; Kitamura et al., 2011; Arima et al., 2011). This disorder encompasses Nakajo-Nishimura syndrome (NKJO); joint contractures, muscular atrophy, microcytic anemia, and panniculitis-induced lipodystrophy (JMP syndrome); and chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperature syndrome (CANDLE). Among Japanese patients, this disorder is best described as Nakajo-Nishimura syndrome, since both Nakajo (1939) and Nishimura et al. (1950) contributed to the original phenotypic descriptions. Genetic Heterogeneity of Proteasome-Associated Autoinflammatory Syndrome See also PRAAS2 (618048), caused by mutation in the POMP gene (613386) on chromosome 13q12; PRAAS3 (617591), caused by mutation in the PSMB4 gene (602177) on chromosome 1q21; PRAAS4 (619183), caused by mutation in the PSMG2 gene (609702) on chromosome 18p11; PRAAS5 (619175), caused by mutation in the PSMB10 gene (176847) on chromosome 16q22; and PRAAS6 (620796), caused by mutation in the PSMB9 gene (177045) on chromosome 6p21.

Proteasome-associated autoinflammatory syndrome-3 (PRAAS3) is an autosomal recessive syndrome with onset in early infancy. Affected individuals present with nodular dermatitis, recurrent fever, myositis, panniculitis-induced lipodystrophy, lymphadenopathy, and dysregulation of the immune response, particularly associated with abnormal type I interferon-induced gene expression patterns. Additional features are highly variable, but may include joint contractures, hepatosplenomegaly, anemia, thrombocytopenia, recurrent infections, autoantibodies, and hypergammaglobulinemia. Some patients may have intracranial calcifications (summary by Brehm et al., 2015). For a discussion of genetic heterogeneity of PRAAS, see PRAAS1 (256040).

Proteasome-associated autoinflammatory syndrome-2 (PRAAS2) is an autosomal dominant disorder with onset in early infancy. Affected individuals develop severe inflammatory neutrophilic dermatitis, autoimmunity, and variable immunodeficiency (summary by Poli et al., 2018). For a discussion of genetic heterogeneity of PRAAS, see PRAAS1 (256040).

Immunodeficiency-63 with lymphoproliferation and autoimmunity (IMD63) is an autosomal recessive disorder characterized by immune dysregulation. Affected individuals present in infancy with features of both abnormal activation of certain immune signaling pathways, resulting in lymphoid proliferation, dermatitis, enteropathy, and hypergammaglobulinemia, as well as features of immunodeficiency, such as recurrent infections and increased susceptibility to viral infections, especially CMV. Laboratory studies show increased NK cells that show impaired differentiation, as well as abnormal T cell populations or responses. Some patients may die in childhood; hematopoietic bone marrow transplantation is curative (summary by Zhang et al., 2019).

Immunodeficiency-64 with lymphoproliferation (IMD64) is an autosomal recessive primary immunodeficiency characterized by onset of recurrent bacterial, viral, and fungal infections in early childhood. Laboratory studies show variably decreased numbers of T cells, with lesser deficiencies of B and NK cells. There is impaired T-cell proliferation and activation; functional defects in B cells and NK cells may also be observed. Patients have increased susceptibility to EBV infection and may develop lymphoproliferation or EBV-associated lymphoma. Some patients may develop features of autoimmunity (summary by Salzer et al., 2016, Mao et al., 2018, and Winter et al., 2018).

Autoinflammation with episodic fever and lymphadenopathy (AIEFL) is an autosomal dominant immunologic disorder characterized by onset of recurrent episodes of unexplained fever beginning in early infancy. The episodes occur in a cyclic pattern with a frequency of every week or every few weeks and a duration of several days. Patients have accompanying lymphadenopathy, and some may have hepatosplenomegaly. Rash and genital ulcers are not observed. Patient serum shows increased levels of inflammatory cytokines and chemokines, including IL6 (147620) and TNF (191160), consistent with abnormal activation of the innate inflammatory system. Treatment with anti-IL6R (147880) antibodies may result in clinical improvement (summary by Lalaoui et al., 2020).

Chronic granulomatous disease (CGD) is a primary immunodeficiency disorder of phagocytes (neutrophils, monocytes, macrophages, and eosinophils) resulting from impaired killing of bacteria and fungi. CGD is characterized by severe recurrent bacterial and fungal infections and dysregulated inflammatory responses resulting in granuloma formation and other inflammatory disorders such as colitis. Infections typically involve the lung (pneumonia), lymph nodes (lymphadenitis), liver (abscess), bone (osteomyelitis), and skin (abscesses or cellulitis). Granulomas typically involve the genitourinary system (bladder) and gastrointestinal tract (often the pylorus initially, and later the esophagus, jejunum, ileum, cecum, rectum, and perirectal area). Some males with X-linked CGD have McLeod neuroacanthocytosis syndrome as the result of a contiguous gene deletion. While CGD may present anytime from infancy to late adulthood, the vast majority of affected individuals are diagnosed before age five years. Use of antimicrobial prophylaxis and therapy has greatly improved overall survival.

X-linked lymphoproliferative disease (XLP) has two recognizable subtypes, XLP1 and XLP2. XLP1 is characterized predominantly by one of three commonly recognized phenotypes: Inappropriate immune response to Epstein-Barr virus (EBV) infection leading to hemophagocytic lymphohistiocytosis (HLH) or severe mononucleosis. Dysgammaglobulinemia. Lymphoproliferative disease (malignant lymphoma). XLP2 is most often characterized by HLH (often associated with EBV), dysgammaglobulinemia, and inflammatory bowel disease. HLH resulting from EBV infection is associated with an unregulated and exaggerated immune response with widespread proliferation of cytotoxic T cells, EBV-infected B cells, and macrophages. Dysgammaglobulinemia is typically hypogammaglobulinemia of one or more immunoglobulin subclasses. The malignant lymphomas are typically B-cell lymphomas, non-Hodgkin type, often extranodal, and in particular involving the intestine.

Immunodeficiency-72 with autoinflammation and lymphoproliferation (IMD72) is an autosomal recessive immunologic disorder characterized by onset of recurrent infections or systemic inflammation in the first year of life. Affected individuals develop bacterial and viral infections that can be severe, including bacteremia, recurrent pneumonia, and meningitis, consistent with an immunodeficiency. There is also an autoimmune and hyperinflammatory aspect to the disorder, manifest as atopy or allergies, hepatosplenomegaly, and lymphoproliferation, including hemophagocytic lymphohistiocytosis (HLH). Immunologic workup shows variable abnormalities, including low or high Ig subsets, increased B cells, irregular T-cell activation and cytokine response, impaired immune synapse formation, and defective cellular migration. At the cellular level, these defects are related to abnormal F-actin polymerization and altered intracellular signaling (summary by Cook et al., 2020).

Immunodeficiency-75 with lymphoproliferation (IMD75) is an autosomal recessive immunologic disorder characterized by immunodeficiency, immune dysregulation, and the development of lymphoproliferative disorders, including lymphoma. Affected individuals usually present in infancy with severe and recurrent infections, mainly viral and affecting the respiratory tract. Some patients may have autoimmune cytopenias, anemia, or thrombocytopenia. Patients also develop hepatosplenomegaly, lymphadenopathy, lymphoproliferative disorders, and various types of T- or B-cell lymphomas. Immunologic work-up shows decreased class-switched B cells, impaired B-cell terminal differentiation, and hypo- or hypergammaglobulinemia. There is skewed differentiation and dysregulation of T cells, as well as possibly disrupted hematopoiesis. Additional features include failure to thrive and global developmental delay. The phenotype may be reminiscent of ALPS (601859), including laboratory evidence of impaired Fas-dependent T-cell apoptosis. Although hematopoietic stem cell transplantation may be effective treatment, many patients die in childhood (summary by Stremenova Spegarova et al., 2020).

Immunodeficiency-76 (IMD76) is an autosomal recessive primary immunologic disorder characterized by onset of recurrent bacterial, viral, and fungal infections in early childhood. Laboratory studies show T-cell lymphopenia and may show variable B-cell or immunoglobulin abnormalities. More variable features found in some patients include lymphoma and neurologic features. Although bone marrow transplantation may be curative, many patients die in childhood (summary by Lyszkiewicz et al., 2020).

Proteasome-associated autoinflammatory syndrome-4 (PRAAS4) is an autosomal recessive immunologic disorder characterized by onset of panniculitis and erythematous skin lesions in early infancy. Additional features include hepatosplenomegaly, lymphadenopathy, fever, generalized lipodystrophy, myositis, and joint contractures, as well as delayed motor and speech development. Autoimmune features, such as hemolytic anemia, may also occur. Laboratory studies show elevation of acute phase reactants and abnormal activation of the type I interferon response. Treatment with the JAK (see 147795) inhibitor ruxolitinib may result in clinical improvement (summary by de Jesus et al., 2019). For a discussion of genetic heterogeneity of PRAAS, see PRAAS1 (256040).

Immunodeficiency-78 with autoimmunity and developmental delay (IMD78) is an autosomal recessive systemic disorder characterized by onset of symptoms in early childhood. Affected individuals present with features of immune deficiency, such as recurrent sinopulmonary or skin infections, as well as autoimmunity, including autoimmune cytopenias, hemolytic anemia, and thrombocytopenia. Autoimmune hepatitis or thyroid disease and central nervous system vasculitis with stroke may also occur. There is increased susceptibility to bacterial, viral, and fungal infections. Laboratory studies show lymphopenia with advanced differentiation and premature senescence of CD8+ T cells and B cells; some patients may have hypergammaglobulinemia. The findings indicate immune dysregulation. Patients also have global developmental delay with speech delay and variable intellectual disability. Many patients die prematurely, but successful hematopoietic bone marrow transplant may be curative (summary by Lu et al., 2014 and Atallah et al., 2021).

Familial autoinflammatory syndrome with or without immunodeficiency (AISIMD) is characterized by onset of various autoimmune features usually in the first decades of life, although later onset has been reported. Typical features include autoimmune cytopenia, hemolytic anemia, thrombocytopenia, and lymphadenopathy. More variable features may include autoimmune thyroiditis, psoriasis or eczema, nephritis, hepatitis, and symptoms of systemic lupus erythematosus (SLE; see 152700). Some patients may have recurrent infections or exacerbation of the disease with acute infection. Laboratory studies show variable findings, often decreased numbers of naive B cells, lymphopenia with skewed subsets, hypogammaglobulinemia, presence of autoantibodies, and a hyperinflammatory state. The disorder shows autosomal dominant inheritance with incomplete penetrance (summary by Hadjadj et al., 2020).

Immunodeficiency-82 with systemic inflammation (IMD82) is a complex autosomal dominant immunologic disorder characterized by recurrent infections with various organisms, as well as noninfectious inflammation manifest as lymphocytic organ infiltration with gastritis, colitis, and lung, liver, CNS, or skin disease. One of the more common features is inflammation of the stomach and bowel. Most patients develop symptoms in infancy or early childhood; the severity is variable. There may be accompanying fever, elevated white blood cell count, decreased B cells, hypogammaglobulinemia, increased C-reactive protein (CRP; 123260), and a generalized hyperinflammatory state. Immunologic workup shows variable B- and T-cell abnormalities such as skewed subgroups. Patients have a propensity for the development of lymphoma, usually in adulthood. At the molecular level, the disorder results from a gain-of-function mutation that leads to constitutive and enhanced activation of the intracellular inflammatory signaling pathway. Treatment with SYK inhibitors rescued human cell abnormalities and resulted in clinical improvement in mice (Wang et al., 2021).

Infantile-onset multisystem neurologic, endocrine, and pancreatic disease-2 (IMNEPD2) is an autosomal recessive multisystemic disorder characterized by cholestatic hepatitis, poor feeding associated with poor overall growth, and hypoglycemia apparent from infancy. Most, but not all, patients have variable global developmental delay. Additional common features include sensorineural deafness, retinal abnormalities with visual defects, and hypotonia. Some patients have endocrine abnormalities, including hyperinsulinemic hypoglycemia, pancreatic dysfunction, hypothyroidism, and primary amenorrhea. Additional features may include hypertriglyceridemia, anemia, proteinuria, increased lactate, and recurrent infections. Brain imaging often shows dysmyelination, thin corpus callosum, cerebral atrophy, and white matter abnormalities. Although the clinical manifestations and severity of the disorder are highly variable, death in early childhood may occur (summary by Williams et al., 2019 and Zeiad et al., 2021). For a discussion of genetic heterogeneity of IMNEPD, see IMNEPD1 (616263).

Immunodeficiency-91 and hyperinflammation (IMD91) is an autosomal recessive complex immunologic disorder characterized by both immunodeficiency and recurrent infections, often to viruses or mycobacteria, as well as by hyperinflammation with systemic involvement. Affected individuals present in infancy with variable features, including fever, infection, thrombocytopenia, renal or hepatic dysfunction, recurrent infections, or seizures. Most patients eventually develop hepatic or renal failure, compromised neurologic function, lymphadenopathy or hepatosplenomegaly, and multiorgan failure resulting in death. More variable features may include intermittent monocytosis, features of hemophagocytic lymphohistiocytosis (HLH), and serologic evidence of hyperinflammation. The disorder is thought to result from dysregulation of the interferon response to viral stimulation in the innate immune system (summary by Le Voyer et al., 2021; Vavassori et al., 2021).

Immunodeficiency-55 is an autosomal recessive primary immunodeficiency characterized by intrauterine growth retardation, natural killer (NK) cell deficiency, and chronic neutropenia. Most patients also have postnatal growth retardation. Other clinical manifestations include mild facial dysmorphism, dry or eczematous skin, and recurrent infections with both viruses and bacteria. The disorder appears to result from a defect in DNA replication causing blockade of immune cell differentiation in the bone marrow, particularly affecting NK cells (summary by Cottineau et al., 2017).

Lymphoproliferative syndrome-3 (LPFS3) is an autosomal recessive early-onset immunologic disorder characterized by increased susceptibility to Epstein-Barr virus (EBV) infection in B cells, resulting in abnormal B-cell proliferation and increased susceptibility to B-cell malignancies, including Hodgkin lymphoma. Patients usually have hypogammaglobulinemia without lymphopenia, although some subsets of immune cells may be low and some patients may have recurrent infections. The disorder results from impaired signaling from proliferating B cells to effector T cells that provide immune surveillance. There may be an increased risk of solid tumors in heterozygous carriers (summary by Abolhassani et al., 2017). For a discussion of genetic heterogeneity of lymphoproliferative syndrome, see XLP1 (308240).

X-linked immunodeficiency-98 with autoinflammation (IMD98) is characterized by onset of recurrent infections associated with lymphoproliferation and autoinflammation in the first decade of life. Mostly males are affected; carrier females may have mild symptoms. Laboratory studies show evidence of immune dysregulation, including hypogammaglobulinemia with reduced memory B cells, skewed T-cell subsets, increased levels of proinflammatory cytokines, activated T cells and monocytes, and autoimmune cytopenias, including neutropenia (Aluri et al., 2021; Fejtkova et al., 2022).

Severe combined immunodeficiency-104 (IMD104) is an autosomal recessive disorder characterized by the onset of recurrent infections in early infancy. Manifestations may include oral thrush, fever, and failure to thrive. Some patients have lymphadenopathy and hepatosplenomegaly, whereas others have absence of lymph nodes and lack a thymic shadow. Laboratory studies show decreased or absent numbers of nonfunctional T cells, normal or increased levels of B cells, variable hypogammaglobulinemia, and normal NK cells. The disorder is caused by a defect in IL7 (146660) signaling due to a mutant IL7 receptor. Hematopoietic stem cell transplantation may be curative (Roifman et al., 2000 and Giliani et al., 2005). Giliani et al. (2005) provided a detailed review of IL7R deficiency, including discussion of the IL7R gene and its function in the immune system, clinical features of the disorder, and experiences with hematopoietic stem cell transplant as treatment. For a general phenotypic description and a discussion of genetic heterogeneity of autosomal recessive SCID, see 601457.

Immunodeficiency-94 with autoinflammation and dysmorphic facies (IMD94) is a systemic immunologic disorder with onset in early infancy. Primary features include lymphadenopathy, autoinflammation, immunodeficiency with hypogammaglobulinemia, and dysmorphic facial features. Intellectual development is normal and serum IgE is not elevated. The disease results from constitutive activation of the IL6 signaling cascade, resulting in immune dysregulation and a hyperinflammatory state (summary by Materna-Kiryluk et al., 2021).

Immunodeficiency-97 with autoinflammation (IMD97) is an autosomal recessive complex immunologic disorder with variable features. Affected individuals present in the first decade of life with inflammatory interstitial lung disease or colitis due to abnormal tissue infiltration by activated T cells. Patients develop autoimmune cytopenias and may have lymphadenopathy; 1 reported patient had features of hemophagocytic lymphohistiocytosis (HLH; see FHL1, 267700). Some patients may have recurrent infections associated with mild lymphopenia, hypogammaglobulinemia, and NK cell dysfunction. Immunologic workup indicates signs of significant immune dysregulation with elevation of inflammatory serum markers, variable immune cell defects involving neutrophils, NK cells, and myeloid cells, and disrupted levels of T regulatory cells (Tregs). Two unrelated patients have been reported (summary by Takeda et al., 2019 and Thian et al., 2020).

Immunodeficiency-99 with hypogammaglobulinemia and autoimmune cytopenias (IMD99) is an autosomal recessive immunologic disorder characterized by the onset of recurrent sinopulmonary infections in early childhood. Laboratory studies reveal hypogammaglobulinemia with decreased memory B cells that show impaired class-switch recombination (CSR) and decreased somatic hypermutation (SHM). Due to abnormal antibody production and impaired self-tolerance, patients may develop autoimmune cytopenias, such as thrombocytopenia, or autoimmune features, such as vitiligo. There are also defects in the T-cell compartment (Kuhny et al., 2020).

X-linked recessive immunodeficiency-118 (IMD118) is characterized by increased susceptibility to the development of disseminated mycobacterial infections in infancy, notably after BCG vaccination. Affected males usually recover with treatment, have no other infections, and show normal growth and development. Immunologic workup shows normal numbers of circulating leukocyte subsets, but functional studies show impaired JAK2 (147796) translation in certain T lymphocytes, resulting in defective IL23 (see 605580)-dependent induction of IFNG (147570) production and secretion from other immune cells (Bohlen et al., 2023).