X-linked agammaglobulinemia (XLA) is characterized by recurrent bacterial infections in affected males in the first two years of life. Recurrent otitis is the most common infection prior to diagnosis. Conjunctivitis, sinopulmonary infections, diarrhea, and skin infections are also frequently seen. Approximately 60% of individuals with XLA are recognized as having immunodeficiency when they develop a severe, life-threatening infection such as pneumonia, empyema, meningitis, sepsis, cellulitis, or septic arthritis. S pneumoniae and H influenzae are the most common organisms found prior to diagnosis and may continue to cause sinusitis and otitis after diagnosis and the initiation of gammaglobulin substitution therapy. Severe, difficult-to-treat enteroviral infections (often manifest as dermatomyositis or chronic meningoencephalitis) can be prevented by this treatment. The prognosis for individuals with XLA has improved markedly in the last 25 years as a result of earlier diagnosis, the development of preparations of gammaglobulin that allow normal concentrations of serum IgG to be achieved, and more liberal use of antibiotics.

The phenotypic spectrum of X-linked severe combined immunodeficiency (X-SCID) ranges from typical X-SCID (early-onset disease in males that is fatal if not treated with hematopoietic stem cell transplantation [HSCT] or gene therapy) to atypical X-SCID (later-onset disease comprising phenotypes caused by variable immunodeficiency, immune dysregulation, and/or autoimmunity). Typical X-SCID. Prior to universal newborn screening (NBS) for SCID most males with typical X-SCID came to medical attention between ages three and six months because of recurrent infections, persistent infections, and infections with opportunistic organisms. With universal NBS for SCID, the common presentation for typical X-SCID is now an asymptomatic, healthy-appearing male infant. Atypical X-SCID, which usually is not detected by NBS, can manifest in the first years of life or later with one of the following: recurrent upper and lower respiratory tract infections with bronchiectasis; Omenn syndrome, a clinical phenotype caused by immune dysregulation; X-SCID combined immunodeficiency (often with recurrent infections, warts, and dermatitis); immune dysregulation and autoimmunity; or Epstein-Barr virus-related lymphoproliferative complications.

An extremely rare type of severe combined immunodeficiency syndrome (SCID) characterized by the classical signs of T-B- SCID (severe and recurrent infections, diarrhea, failure to thrive, absence of T and B lymphocytes) associated with skeletal anomalies like short stature, bowing of the long bones and metaphyseal abnormalities of variable degree of severity.

A rare autosomal recessive primary immunodeficiency characterized by absence of HLA class II molecules on the surface of immune cells, leading to severely impaired cellular and humoral immune response to foreign antigens, severe CD4+ T-cell lymphopenia, and hypogammaglobulinemia. The disease clinically manifests with early onset of severe and recurrent infections mainly of the respiratory and gastrointestinal tract, protracted diarrhea with failure to thrive, and autoimmune disease, and is frequently fatal in childhood.

Any autosomal agammaglobulinemia in which the cause of the disease is a mutation in the CD79B gene.

Any autosomal agammaglobulinemia in which the cause of the disease is a mutation in the IGLL1 gene.

Any autosomal agammaglobulinemia in which the cause of the disease is a mutation in the CD79A gene.

Any autosomal agammaglobulinemia in which the cause of the disease is a mutation in the BLNK gene.

Any autosomal agammaglobulinemia in which the cause of the disease is a mutation in the LRRC8A gene.

Agammaglobulinemia is a primary immunodeficiency characterized by profoundly low or absent serum antibodies and low or absent circulating B cells due to an early block of B-cell development. Affected individuals develop severe infections in the first years of life. The most common form of agammaglobulinemia is X-linked agammaglobulinemia (AGMX1, XLA; 300755), also known as Bruton disease, which is caused by mutation in the BTK gene (300300). AGMX1 accounts for anywhere from 85 to 95% of males who have the characteristic findings (Lopez Granados et al., 2002; Ferrari et al., 2007). Autosomal recessive inheritance of agammaglobulinemia, which has a similar phenotype to that of the X-linked form, has been observed in a small number of families, and accounts for up to 15% of patients with agammaglobulinemia (Ferrari et al., 2007). Conley (1999) gave a comprehensive review of autosomal recessive agammaglobulinemia. Genetic Heterogeneity of Autosomal Agammaglobulinemia Autosomal agammaglobulinemia is a genetically heterogeneous disorder: see also AGM2 (613500), caused by mutation in the IGLL1 gene (146770); AGM3 (613501), caused by mutation in the CD79A gene (112205); AGM4 (613502), caused by mutation in the BLNK gene (604515); AGM5 (613506), caused by disruption of the LRRC8 gene (608360); AGM6 (612692), caused by mutation in the CD79B gene (147245); AGM7 (615214), caused by mutation in the PIK3R1 gene (171833); AGM8 (616941), caused by mutation in the TCF3 gene (147141); AGM9 (619693), caused by mutation in the SLC39A7 gene (601416); and AGM10 (619707), caused by mutation in the SPI1 gene (165170).

Immunodeficiency-11A is an autosomal recessive primary immunodeficiency characterized by normal numbers of T and B lymphocytes, but defective intracellular signaling. There is a block in B-cell differentiation with increased numbers of transitional B cells and hypogammaglobulinemia, as well as decreased numbers of regulatory T cells and defects in T-cell function (summary by Greil et al., 2013 and Stepensky et al., 2013).

Any autosomal agammaglobulinemia in which the cause of the disease is a mutation in the PIK3R1 gene.

Any autosomal agammaglobulinemia in which the cause of the disease is a mutation in the TCF3 gene.

Immunodeficiency-centromeric instability-facial anomalies syndrome-4 is an autosomal recessive disorder characterized by recurrent infections in childhood and variable dysmorphic facial features. Laboratory studies show hypomethylation of certain chromosomal regions. Additional features, including delayed development, are variable (summary by Thijssen et al., 2015). For a discussion of genetic heterogeneity of immunodeficiency-centromeric instability-facial anomalies syndrome, see ICF1 (242860).

Immunodeficiency-centromeric instability-facial anomalies syndrome-3 is an autosomal recessive disorder characterized by recurrent infections in childhood and variable dysmorphic facial features. Laboratory studies show hypomethylation of certain chromosomal regions. Additional features, including delayed development, are variable (summary by Thijssen et al., 2015). For a discussion of genetic heterogeneity of immunodeficiency-centromeric instability-facial anomalies syndrome, see ICF1 (242860).

Immunodeficiency-15B (IMD15B) is an autosomal recessive primary immunodeficiency disorder characterized by onset in infancy of life-threatening bacterial, fungal, and viral infections and failure to thrive. Laboratory studies show hypo- or agammaglobulinemia with relatively normal numbers of B and T cells. However, functional studies show impaired differentiation and activation of immune cells (summary by Pannicke et al., 2013).

Agammaglobulinemia-9 (AGM9) is an autosomal recessive primary immunodeficiency characterized by recurrent bacterial infections associated with agammaglobulinemia and absence of circulating B cells. Additional features include failure to thrive and skin involvement. The severity is variable: more severe cases may require hematopoietic stem cell transplantation, whereas others can be treated effectively with Ig replacement therapy (summary by Anzilotti et al., 2019). For a discussion of genetic heterogeneity of autosomal agammaglobulinemia, see AGM1 (601495).

Immunodeficiency-93 and hypertrophic cardiomyopathy (IMD93) is an autosomal recessive disorder characterized by onset of recurrent viral and bacterial infections, particularly with encapsulated bacteria, and hypertrophic cardiomyopathy in the first months or years of life. Immunologic workup typically shows decreased circulating B cells and hypo- or agammaglobulinemia, sometimes with neutropenia or T-cell lymphocytosis, although laboratory findings may be variable among patients. Ig replacement therapy is beneficial. Cardiac involvement can also include atrial septal defect, valvular insufficiency, and pre-excitation syndrome. Rare myopathic or neurologic involvement has been reported, but these features are not consistently part of the disorder and may be related to other genetic defects (summary by Niehues et al., 2020 and Saettini et al., 2021).

Autosomal dominant agammaglobulinemia-10 (AGM10) is characterized by early-childhood onset of recurrent viral and bacterial infections affecting various organ systems, particularly the sinopulmonary system. Laboratory studies show low or absent circulating B cells and hypo- or agammaglobulinemia. Affected individuals may have adverse reactions to certain vaccinations, such as the polio vaccine. Treatment with replacement Ig is effective; hematopoietic stem cell transplantation has also been reported (summary by Le Coz et al., 2021). For a discussion of genetic heterogeneity of autosomal agammaglobulinemia, see AGM1 (601495).

Autosomal recessive agammaglobulinemia-8B (AGM8B) is characterized by onset of recurrent infections in early childhood. Laboratory studies of affected individuals show decreased circulating immunoglobulins and decreased peripheral B cells. More variable features may include dysmorphic facies and subtle abnormalities of other immune cells, such as T cells. One patient who developed childhood B-cell acute lymphocytic leukemia (B-ALL) has been described (summary by Ben-Ali et al., 2017).

Gastrointestinal defects and immunodeficiency syndrome-1 (GIDID1) is characterized by multiple intestinal atresia, in which atresia occurs at various levels throughout the small and large intestines. Surgical outcomes are poor, and the condition is usually fatal within the first month of life. Some patients exhibit inflammatory bowel disease (IBD), with or without intestinal atresia, and in some cases, the intestinal features are associated with either mild or severe combined immunodeficiency (Samuels et al., 2013; Avitzur et al., 2014; Lemoine et al., 2014). Genetic Heterogeneity of GIDID See also GIDID2 (619708), caused by mutation in the PI4KA gene (600286) on chromosome 22q11.