Pompe disease is classified by age of onset, organ involvement, severity, and rate of progression. Infantile-onset Pompe disease (IOPD; individuals with onset before age 12 months with cardiomyopathy) may be apparent in utero but more typically onset is at the median age of four months with hypotonia, generalized muscle weakness, feeding difficulties, failure to thrive, respiratory distress, and hypertrophic cardiomyopathy. Without treatment by enzyme replacement therapy (ERT), IOPD commonly results in death by age two years from progressive left ventricular outflow obstruction and respiratory insufficiency. Late-onset Pompe disease (LOPD; including: (a) individuals with onset before age 12 months without cardiomyopathy; and (b) all individuals with onset after age 12 months) is characterized by proximal muscle weakness and respiratory insufficiency; clinically significant cardiac involvement is uncommon.

Intracranial berry aneurysms are saccular outpouchings of the intracranial arteries, most commonly at arterial bifurcations, characterized by arterial wall remodeling. Most cases of ruptured intracranial berry aneurysms result in a subarachnoid hemorrhage, associated with high morbidity and mortality (summary by van der Voet et al., 2004). For a discussion of genetic heterogeneity of intracranial berry aneurysm, see ANIB1 (105800).

Hereditary hemorrhagic telangiectasia (HHT) is characterized by the presence of multiple arteriovenous malformations (AVMs) that lack intervening capillaries and result in direct connections between arteries and veins. The most common clinical manifestation is spontaneous and recurrent nosebleeds (epistaxis) beginning on average at age 12 years. Telangiectases (small AVMs) are characteristically found on the lips, tongue, buccal and gastrointestinal (GI) mucosa, face, and fingers. The appearance of telangiectases is generally later than epistaxis but may be during childhood. Large AVMs occur most often in the lungs, liver, or brain; complications from bleeding or shunting may be sudden and catastrophic. A minority of individuals with HHT have GI bleeding, which is rarely seen before age 50 years.

A rare systemic disease characterized by progressive hyalinosis involving capillaries, arterioles and small veins of the digestive tract, kidneys, and retina, associated with idiopathic cerebral calcifications, manifesting with severe diarrhea (with rectal bleeding and malabsorption), nephropathy (with renal failure and systemic hypertension), chorioretinal scarring, and subarachnoid hemorrhage. Poikiloderma and premature greying of the hair may be additionally observed.

Hereditary hemorrhagic telangiectasia (HHT) is characterized by the presence of multiple arteriovenous malformations (AVMs) that lack intervening capillaries and result in direct connections between arteries and veins. The most common clinical manifestation is spontaneous and recurrent nosebleeds (epistaxis) beginning on average at age 12 years. Telangiectases (small AVMs) are characteristically found on the lips, tongue, buccal and gastrointestinal (GI) mucosa, face, and fingers. The appearance of telangiectases is generally later than epistaxis but may be during childhood. Large AVMs occur most often in the lungs, liver, or brain; complications from bleeding or shunting may be sudden and catastrophic. A minority of individuals with HHT have GI bleeding, which is rarely seen before age 50 years.

Stormorken syndrome is an autosomal dominant disorder characterized by mild bleeding tendency due to platelet dysfunction, thrombocytopenia, anemia, asplenia, tubular aggregate myopathy, congenital miosis, and ichthyosis. Additional features may include headache or recurrent stroke-like episodes (summary by Misceo et al., 2014).

Two types of hereditary cerebral amyloid angiopathy, known as familial British dementia and familial Danish dementia, are characterized by dementia and movement problems. Strokes are uncommon in these types. People with the Danish type also have clouding of the lens of the eyes (cataracts) and deafness.\n\nStrokes are rare in people with the Arctic type of hereditary cerebral amyloid angiopathy, in which the first sign is usually memory loss that then progresses to severe dementia. Strokes are also uncommon in individuals with the Iowa type. This type is characterized by memory loss, problems with vocabulary and the production of speech, personality changes, and involuntary muscle twitches (myoclonus).\n\nThe first sign of the Icelandic type of hereditary cerebral amyloid angiopathy is typically a stroke followed by dementia. Strokes associated with the Icelandic type usually occur earlier than the other types, with individuals typically experiencing their first stroke in their twenties or thirties.\n\nPeople with the Flemish and Italian types of hereditary cerebral amyloid angiopathy are prone to recurrent strokes and dementia. Individuals with the Piedmont type may have one or more strokes and typically experience impaired movements, numbness or tingling (paresthesias), confusion, or dementia.\n\nThe Dutch type of hereditary cerebral amyloid angiopathy is the most common form. Stroke is frequently the first sign of the Dutch type and is fatal in about one third of people who have this condition. Survivors often develop dementia and have recurrent strokes. About half of individuals with the Dutch type who have one or more strokes will have recurrent seizures (epilepsy).\n\nThere are many different types of hereditary cerebral amyloid angiopathy. The different types are distinguished by their genetic cause, which determines whether areas of the brain other than blood vessels are affected, and the signs and symptoms that occur. The various types of hereditary cerebral amyloid angiopathy are named after the regions where they were first diagnosed.\n\nHereditary cerebral amyloid angiopathy is a condition characterized by an abnormal buildup of protein clumps called amyloid deposits in the blood vessels in the brain, causing vascular disease (angiopathy). People with hereditary cerebral amyloid angiopathy often have progressive loss of intellectual function (dementia), stroke, and other neurological problems starting in mid-adulthood. Due to neurological decline, this condition is typically fatal in one's sixties, although there is variation depending on the severity of the signs and symptoms. Most affected individuals die within a decade after signs and symptoms first appear, although some people with the disease have survived longer.

Loeys-Dietz syndrome (LDS) is characterized by vascular findings (cerebral, thoracic, and abdominal arterial aneurysms and/or dissections), skeletal manifestations (pectus excavatum or pectus carinatum, scoliosis, joint laxity, arachnodactyly, talipes equinovarus, and cervical spine malformation and/or instability), craniofacial features (hypertelorism, strabismus, bifid uvula / cleft palate, and craniosynostosis that can involve any sutures), and cutaneous findings (velvety and translucent skin, easy bruising, and dystrophic scars). Individuals with LDS are predisposed to widespread and aggressive arterial aneurysms and pregnancy-related complications including uterine rupture and death. Individuals with LDS can show a strong predisposition for allergic/inflammatory disease including asthma, eczema, and reactions to food or environmental allergens. There is also an increased incidence of gastrointestinal inflammation including eosinophilic esophagitis and gastritis or inflammatory bowel disease. Wide variation in the distribution and severity of clinical features can be seen in individuals with LDS, even among affected individuals within a family who have the same pathogenic variant.

Hereditary hemorrhagic telangiectasia (HHT) is characterized by the presence of multiple arteriovenous malformations (AVMs) that lack intervening capillaries and result in direct connections between arteries and veins. The most common clinical manifestation is spontaneous and recurrent nosebleeds (epistaxis) beginning on average at age 12 years. Telangiectases (small AVMs) are characteristically found on the lips, tongue, buccal and gastrointestinal (GI) mucosa, face, and fingers. The appearance of telangiectases is generally later than epistaxis but may be during childhood. Large AVMs occur most often in the lungs, liver, or brain; complications from bleeding or shunting may be sudden and catastrophic. A minority of individuals with HHT have GI bleeding, which is rarely seen before age 50 years.

Hyper-IgE syndrome-2 with recurrent infections (HIES2) is an autosomal recessive immunologic disorder characterized by recurrent staphylococcal infections of the skin and respiratory tract, eczema, elevated serum immunoglobulin E, and hypereosinophilia. It is distinguished from autosomal dominant HIES1 (147060) by the lack of connective tissue and skeletal involvement (Renner et al., 2004). For a discussion of genetic heterogeneity of hyper-IgE syndrome, see 147060. See also TYK2 deficiency (611521), a clinically distinct disease entity that includes characteristic features of both autosomal recessive HIES2 and mendelian susceptibility to mycobacterial disease (MSMD; 209950) (Minegishi et al., 2006).

Rupture of an intracranial aneurysm (IA), an outpouching or sac-like widening of a cerebral artery, leads to a subarachnoid hemorrhage (SAH), a sudden-onset disease that can lead to severe disability and death. Several risk factors such as smoking, hypertension, and excessive alcohol intake are associated with subarachnoid hemorrhage (summary by Krischek and Inoue, 2006).

X-linked syndromic intellectual developmental disorder-37 (MRXS37) is a developmental disorder showing phenotypic variability and variable severity. Male mutation carriers tend to be more severely affected than female mutation carriers, some of whom may even be asymptomatic. In general, the disorder is characterized by global developmental delay with delayed walking, speech delay, impaired intellectual development that ranges from borderline low to moderate, and behavioral abnormalities, such as autism and sleeping difficulties. Many patients are able to attend mainstream schools with assistance and work under supervision. Additional more variable features include sensorineural hearing loss, ocular anomalies, feeding difficulties, dysmorphic facial features, inguinal and umbilical hernia, genitourinary defects, congenital heart defects, musculoskeletal anomalies, and endocrine dysfunction, such as hypogonadism or hyperparathyroidism (Shepherdson et al., 2024).