An instance of thrombophilia that is inherited. [from MONDO]

BRCA1- and BRCA2-associated hereditary breast and ovarian cancer (HBOC) is characterized by an increased risk for female and male breast cancer, ovarian cancer (including fallopian tube and primary peritoneal cancers), and to a lesser extent other cancers such as prostate cancer, pancreatic cancer, and melanoma primarily in individuals with a BRCA2 pathogenic variant. The risk of developing an associated cancer varies depending on whether HBOC is caused by a BRCA1 or BRCA2 pathogenic variant. [from GeneReviews]

A small percentage of all breast cancers cluster in families. These cancers are described as hereditary and are associated with inherited gene mutations. Hereditary breast cancers tend to develop earlier in life than noninherited (sporadic) cases, and new (primary) tumors are more likely to develop in both breasts.\n\nIn some cases, cancerous cells can invade surrounding breast tissue. In these cases, the condition is known as invasive breast cancer. Sometimes, tumors spread to other parts of the body. If breast cancer spreads, cancerous cells most often appear in the bones, liver, lungs, or brain. Tumors that begin at one site and then spread to other areas of the body are called metastatic cancers.\n\nIn its early stages, breast cancer usually does not cause pain and may exhibit no noticeable symptoms. As the cancer progresses, signs and symptoms can include a lump or thickening in or near the breast; a change in the size or shape of the breast; nipple discharge, tenderness, or retraction (turning inward); and skin irritation, dimpling, redness, or scaliness. However, these changes can occur as part of many different conditions. Having one or more of these symptoms does not mean that a person definitely has breast cancer.\n\nBreast cancer is a disease in which certain cells in the breast become abnormal and multiply uncontrollably to form a tumor. Although breast cancer is much more common in women, this form of cancer can also develop in men. In both women and men, the most common form of breast cancer begins in cells lining the milk ducts (ductal cancer). In women, cancer can also develop in the glands that produce milk (lobular cancer). Most men have little or no lobular tissue, so lobular cancer in men is very rare. [from MedlinePlus Genetics]

Methylenetetrahydrofolate Reductase (MTHFR) Deficiency is the most common genetic cause of elevated levels of homocysteine in the plasma (hyperhomocysteinemia). The MTHFR enzyme plays an important role in processing amino acids, specifically, the conversion of homocysteine to methionine. Genetic variations in the MTHFR gene can lead to impaired function or inactivation of this enzyme, which results in mildly elevated levels of homocysteine, especially in individuals who are also deficient in folate. In these individuals, a daily supplement of low dose folic acid may reduce and often normalize their homocysteine levels, but this has not been demonstrated to improve health outcomes. A common genetic variant in the MTHFR gene is a 677C>T polymorphism (NM_005957.4:c.665C>T, rs1801133). This variant encodes a thermolabile enzyme that is less active at higher temperatures. Individuals who carry two copies of this variant (“TT homozygous”) tend to have higher homocysteine levels and lower serum folate levels compared to controls. More than 25% of Hispanics and around 10-15% of North America Caucasians are estimated to be homozygous for the “thermolabile” variant (TT genotype). The TT genotype is least common in individuals of African descent (6%). Another common MTHFR variant, 1298A>C (NM_005957.4:c.1286A>C, rs1801131), does not cause increased homocysteine levels in heterozygous or homozygous individuals, but combined heterozygosity of 1298A>C and 677C>T results in an outcome similar to TT homozygous individuals. Until recently, it was thought that MTHFR deficiency, by causing elevated homocysteine levels, led to an increased risk of venous thrombosis, coronary heart disease, and recurrent pregnancy loss. However, more recent analysis has not found an association between elevated homocysteine levels and the risk of venous thrombosis or the risk of coronary heart disease. MTHFR polymorphism genotyping should not be ordered as part of the clinical evaluation for thrombophilia, recurrent pregnancy loss, or for at-risk family members. Rarely, more severe variants in the MTHFR gene can be a cause of an autosomal recessive inborn error or metabolism where extremely high levels of homocysteine accumulate in the urine and plasma. This can cause developmental delay, eye disorders, thrombosis, and osteoporosis. But more commonly, homocystinuria is caused by variants in a different gene (cystathionine beta-synthase, CBS). [from Medical Genetics Summaries]

Charcot-Marie-Tooth disease constitutes a clinically and genetically heterogeneous group of hereditary motor and sensory neuropathies. On the basis of electrophysiologic criteria, CMT is divided into 2 major types: type 1, the demyelinating form, characterized by a motor median nerve conduction velocity less than 38 m/s (see CMT1B; 118200); and type 2, the axonal form, with a normal or slightly reduced nerve conduction velocity. For a phenotypic description and a discussion of genetic heterogeneity of axonal CMT type 2, see CMT2A1 (118210). [from OMIM]

A rare autosomal dominant form of heart-hand syndrome, first described in members of a Slovenian family. The syndrome has characteristics of adult onset, progressive cardiac conduction disease, tachyarrhythmias that can lead to sudden death, dilated cardiomyopathy and brachydactyly, with the hands less severely affected than the feet. Muscle weakness and/or myopathic electromyographic findings have been observed in some cases. [from SNOMEDCT_US]

A chromosomal abnormality consisting of the presence of a third copy of chromosome 16 in somatic cells. [from NCI]

LMNA-related dilated cardiomyopathy (DCM) is characterized by left ventricular enlargement and/or reduced systolic function preceded (sometimes by many years) by or accompanied by conduction system disease and/or arrhythmias. LMNA-related DCM usually presents in early to mid-adulthood with symptomatic conduction system disease or arrhythmias, or with symptomatic DCM including heart failure or embolus from a left ventricular mural thrombus. Sudden cardiac death can occur, and in some instances is the presenting manifestation; sudden cardiac death may occur with minimal or no systolic dysfunction. [from GeneReviews]

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. [from GeneReviews]

Smith-Magenis syndrome (SMS) is characterized by distinctive physical features (particularly coarse facial features that progress with age), developmental delay, cognitive impairment, behavioral abnormalities, sleep disturbance, and childhood-onset abdominal obesity. Infants have feeding difficulties, failure to thrive, hypotonia, hyporeflexia, prolonged napping or need to be awakened for feeds, and generalized lethargy. The majority of individuals function in the mild-to-moderate range of intellectual disability. The behavioral phenotype, including significant sleep disturbance, stereotypies, and maladaptive and self-injurious behaviors, is generally not recognized until age 18 months or older and continues to change until adulthood. Sensory issues are frequently noted; these may include avoidant behavior, as well as repetitive seeking of textures, sounds, and experiences. Toileting difficulties are common. Significant anxiety is common as are problems with executive functioning, including inattention, distractibility, hyperactivity, and impulsivity. Maladaptive behaviors include frequent outbursts / temper tantrums, attention-seeking behaviors, opposition, aggression, and self-injurious behaviors including self-hitting, self-biting, skin picking, inserting foreign objects into body orifices (polyembolokoilamania), and yanking fingernails and/or toenails (onychotillomania). Among the stereotypic behaviors described, the spasmodic upper-body squeeze or "self-hug" seems to be highly associated with SMS. An underlying developmental asynchrony, specifically emotional maturity delayed beyond intellectual functioning, may also contribute to maladaptive behaviors in people with SMS. [from GeneReviews]

BRCA1- and BRCA2-associated hereditary breast and ovarian cancer (HBOC) is characterized by an increased risk for female and male breast cancer, ovarian cancer (including fallopian tube and primary peritoneal cancers), and to a lesser extent other cancers such as prostate cancer, pancreatic cancer, and melanoma primarily in individuals with a BRCA2 pathogenic variant. The risk of developing an associated cancer varies depending on whether HBOC is caused by a BRCA1 or BRCA2 pathogenic variant. [from GeneReviews]

Succinic semialdehyde dehydrogenase (SSADH) deficiency is characterized by infantile-onset hypotonia, developmental delay, cognitive impairment, expressive language deficit, and mild ataxia. Epilepsy is present in about half of affected individuals and is more common in adults. Hyperkinetic behavior, aggression, self-injurious behaviors, hallucinations, and sleep disturbances have been reported in nearly half of all affected individuals, more commonly in those who are older. Basal ganglia signs including choreoathetosis, dystonia, and myoclonus have been reported in a few individuals with earlier-onset, more severe disease. Involvement beyond the central nervous system has not been described. Individuals with SSADH deficiency typically have 4-hydroxybutyric aciduria present on urine organic acid analysis. Head MRI reveals T2 hyperintensities in multiple regions, involving the globus pallidi, cerebellar dentate nuclei, subthalamic nuclei, subcortical white matter, and brain stem, as well as cerebral and sometimes cerebellar atrophy. EEG findings include background slowing and spike discharges that are usually generalized. [from GeneReviews]

Restrictive dermopathy is a rare, lethal genodermatosis with characteristic manifestations that are easily recognizable at birth: thin, tightly adherent translucent skin with erosions at flexure sites, superficial vessels, typical facial dysmorphism, and generalized joint ankylosis. Prenatal signs can include intrauterine growth retardation, reduced fetal movements, polyhydramnios, and premature rupture of the membranes. Most infants die within the first week of life (summary by Smigiel et al., 2010). Genetic Heterogeneity of Restrictive Dermopathy See also RSMD2 (619793), caused by mutation in the LMNA gene (150330) on chromosome 1q22. [from OMIM]

Emery-Dreifuss muscular dystrophy (EDMD) is characterized by the clinical triad of: joint contractures that begin in early childhood; slowly progressive muscle weakness and wasting initially in a humero-peroneal distribution that later extends to the scapular and pelvic girdle muscles; and cardiac involvement that may manifest as palpitations, presyncope and syncope, poor exercise tolerance, and congestive heart failure along with variable cardiac rhythm disturbances. Age of onset, severity, and progression of muscle and cardiac involvement demonstrate both inter- and intrafamilial variability. Clinical variability ranges from early onset with severe presentation in childhood to late onset with slow progression in adulthood. In general, joint contractures appear during the first two decades, followed by muscle weakness and wasting. Cardiac involvement usually occurs after the second decade and respiratory function may be impaired in some individuals. [from GeneReviews]

Triple A syndrome is an inherited condition characterized by three specific features: achalasia, Addison disease, and alacrima. Achalasia is a disorder that affects the ability to move food through the esophagus, the tube that carries food from the throat to the stomach. It can lead to severe feeding difficulties and low blood glucose (hypoglycemia). Addison disease, also known as primary adrenal insufficiency, is caused by abnormal function of the small hormone-producing glands on top of each kidney (adrenal glands). The main features of Addison disease include fatigue, loss of appetite, weight loss, low blood pressure, and darkening of the skin. The third major feature of triple A syndrome is a reduced or absent ability to secrete tears (alacrima). Most people with triple A syndrome have all three of these features, although some have only two.\n\nMany of the features of triple A syndrome are caused by dysfunction of the autonomic nervous system. This part of the nervous system controls involuntary body processes such as digestion, blood pressure, and body temperature. People with triple A syndrome often experience abnormal sweating, difficulty regulating blood pressure, unequal pupil size (anisocoria), and other signs and symptoms of autonomic nervous system dysfunction (dysautonomia).\n\nPeople with this condition may have other neurological abnormalities, such as developmental delay, intellectual disability, speech problems (dysarthria), and a small head size (microcephaly). In addition, affected individuals commonly experience muscle weakness, movement problems, and nerve abnormalities in their extremities (peripheral neuropathy). Some develop optic atrophy, which is the degeneration (atrophy) of the nerves that carry information from the eyes to the brain. Many of the neurological symptoms of triple A syndrome worsen over time.\n\nPeople with triple A syndrome frequently develop a thickening of the outer layer of skin (hyperkeratosis) on the palms of their hands and the soles of their feet. Other skin abnormalities may also be present in people with this condition.\n\nAlacrima is usually the first noticeable sign of triple A syndrome, as it becomes apparent early in life that affected children produce little or no tears while crying. They develop Addison disease and achalasia during childhood or adolescence, and most of the neurologic features of triple A syndrome begin during adulthood. The signs and symptoms of this condition vary among affected individuals, even among members of the same family. [from MedlinePlus Genetics]

The term "galactosemia" refers to disorders of galactose metabolism that include classic galactosemia, clinical variant galactosemia, and biochemical variant galactosemia (not covered in this chapter). This GeneReview focuses on: Classic galactosemia, which can result in life-threatening complications including feeding problems, failure to thrive, hepatocellular damage, bleeding, and E coli sepsis in untreated infants. If a lactose-restricted diet is provided during the first ten days of life, the neonatal signs usually quickly resolve and the complications of liver failure, sepsis, and neonatal death are prevented; however, despite adequate treatment from an early age, children with classic galactosemia remain at increased risk for developmental delays, speech problems (termed childhood apraxia of speech and dysarthria), and abnormalities of motor function. Almost all females with classic galactosemia manifest hypergonadatropic hypogonadism or premature ovarian insufficiency (POI). Clinical variant galactosemia, which can result in life-threatening complications including feeding problems, failure to thrive, hepatocellular damage including cirrhosis, and bleeding in untreated infants. This is exemplified by the disease that occurs in African Americans and native Africans in South Africa. Persons with clinical variant galactosemia may be missed with newborn screening as the hypergalactosemia is not as marked as in classic galactosemia and breath testing is normal. If a lactose-restricted diet is provided during the first ten days of life, the severe acute neonatal complications are usually prevented. African Americans with clinical variant galactosemia and adequate early treatment do not appear to be at risk for long-term complications, including POI. [from GeneReviews]

PAFAH1B1-related lissencephaly/subcortical band heterotopia (SBH) comprises a spectrum of severity. Affected newborns typically have mild-to-moderate hypotonia, feeding difficulties, and poor head control. During the first years, neurologic examination typically demonstrates poor visual tracking and response to sounds, axial hypotonia, and mild distal spasticity that can transition over time to more severe spasticity. Seizures occur in more than 90% of individuals with lissencephaly and often include infantile spasms. Seizures are often drug resistant, but even with good seizure control, the best developmental level achieved (excluding the few individuals with partial lissencephaly) is the equivalent of about age three to five months. In individuals with PAFAH1B1-related lissencephaly/SBH, developmental delay ranges from mild to severe. Other findings in PAFAH1B1-related lissencephaly/SBH include feeding issues and aspiration (which may result in need for gastrostomy tube placement), progressive microcephaly, and occasional developmental regression. [from GeneReviews]