Lymphedema-distichiasis syndrome (referred to as LDS in this GeneReview) is characterized by lower-limb lymphedema, and distichiasis (aberrant eyelashes ranging from a full set of extra eyelashes to a single hair). Lymphedema typically appears in late childhood or puberty, is confined to the lower limbs with or without involvement of the external genitalia, and is often asymmetric; severity varies within families. Males develop edema at an earlier age and have more problems with cellulitis than females. Distichiasis, which may be present at birth, is observed in 94% of affected individuals. About 75% of affected individuals have ocular findings including corneal irritation, recurrent conjunctivitis, and photophobia; other common findings include varicose veins and ptosis.

Netherton syndrome is a disorder that affects the skin, hair, and immune system. Newborns with Netherton syndrome have skin that is red and scaly (ichthyosiform erythroderma), and the skin may leak fluid. Some affected infants are born with a tight, clear sheath covering their skin called a collodion membrane. This membrane is usually shed during the first few weeks of life. Because newborns with this disorder are missing the protection provided by normal skin, they are at risk of becoming dehydrated and developing infections in the skin or throughout the body (sepsis), which can be life-threatening. Affected babies may also fail to grow and gain weight at the expected rate (failure to thrive). The health of older children and adults with Netherton syndrome usually improves, although they often remain underweight and of short stature.\n\nAfter infancy, the severity of the skin abnormalities varies among people with Netherton syndrome and can fluctuate over time. The skin may continue to be red and scaly, especially during the first few years of life. Some affected individuals have intermittent redness or experience outbreaks of a distinctive skin abnormality called ichthyosis linearis circumflexa, involving patches of multiple ring-like lesions. The triggers for the outbreaks are not known, but researchers suggest that stress or infections may be involved.\n\nItchiness is a common problem for affected individuals, and scratching can lead to frequent infections. Dead skin cells are shed at an abnormal rate and often accumulate in the ear canals, which can affect hearing if not removed regularly. The skin is abnormally absorbent of substances such as lotions and ointments, which can result in excessive blood levels of some topical medications. Because the ability of the skin to protect against heat and cold is impaired, affected individuals may have difficulty regulating their body temperature.\n\nPeople with Netherton syndrome have hair that is fragile and breaks easily. Some strands of hair vary in diameter, with thicker and thinner spots. This feature is known as bamboo hair, trichorrhexis nodosa, or trichorrhexis invaginata. In addition to the hair on the scalp, the eyelashes and eyebrows may be affected. The hair abnormality in Netherton syndrome may not be noticed in infancy because babies often have sparse hair.\n\nMost people with Netherton syndrome have immune system-related problems such as food allergies, hay fever, asthma, or an inflammatory skin disorder called eczema.

Episodic ataxia type 1 (EA1) is a potassium channelopathy characterized by constant myokymia and dramatic episodes of spastic contractions of the skeletal muscles of the head, arms, and legs with loss of both motor coordination and balance. During attacks individuals may experience a number of variable symptoms including vertigo, blurred vision, diplopia, nausea, headache, diaphoresis, clumsiness, stiffening of the body, dysarthric speech, and difficulty in breathing, among others. EA1 may be associated with epilepsy. Other possible associations include delayed motor development, cognitive disability, choreoathetosis, and carpal spasm. Usually, onset is in childhood or early adolescence.

Familial partial lipodystrophy type 1 (FPLD1), or Kobberling-type lipodystrophy, is characterized by loss of adipose tissue confined to the extremities, with normal or increased distribution of fat on the face, neck, and trunk (Kobberling and Dunnigan, 1986). For a general description and a discussion of genetic heterogeneity of familial partial lipodystrophy (FPLD), see 151660.

Satoyoshi syndrome is a rare disorder characterized by progressive, painful, intermittent muscle spasms, diarrhea or unusual malabsorption, endocrinopathy with amenorrhea, and secondary skeletal abnormalities. The disorder is also called komuragaeri disease by the Japanese; in Japanese 'komura' means calf and 'gaeri' means 'turnover' or spasm. All cases have apparently been sporadic, even when occurring in large families (Ehlayel and Lacassie, 1995).

The WAS-related disorders, which include Wiskott-Aldrich syndrome, X-linked thrombocytopenia (XLT), and X-linked congenital neutropenia (XLN), are a spectrum of disorders of hematopoietic cells, with predominant defects of platelets and lymphocytes caused by pathogenic variants in WAS. WAS-related disorders usually present in infancy. Affected males have thrombocytopenia with intermittent mucosal bleeding, bloody diarrhea, and intermittent or chronic petechiae and purpura; eczema; and recurrent bacterial and viral infections, particularly of the ear. At least 40% of those who survive the early complications develop one or more autoimmune conditions including hemolytic anemia, immune thrombocytopenic purpura, immune-mediated neutropenia, rheumatoid arthritis, vasculitis, and immune-mediated damage to the kidneys and liver. Individuals with a WAS-related disorder, particularly those who have been exposed to Epstein-Barr virus (EBV), are at increased risk of developing lymphomas, which often occur in unusual, extranodal locations including the brain, lung, or gastrointestinal tract. Males with XLT have thrombocytopenia with small platelets; other complications of Wiskott-Aldrich syndrome, including eczema and immune dysfunction, are usually mild or absent. Males with XLN have congenital neutropenia, myeloid dysplasia, and lymphoid cell abnormalities.

Digital extensor muscle aplasia-polyneuropathy is a rare, hereditary motor and sensory neuropathy characterized by flexion deformities of the thumb and fingers, sensory deficit in the hand and polyneuropathic electrophysiologic findings in the limbs. Operation on the hands reveals extensor muscles and their tendons to be absent or hypoplastic. There have been no further descriptions in the literature since 1986.

Cerebral cavernous malformations (CCMs) are vascular malformations in the brain and spinal cord comprising closely clustered, enlarged capillary channels (caverns) with a single layer of endothelium without mature vessel wall elements or normal intervening brain parenchyma. The diameter of CCMs ranges from a few millimeters to several centimeters. CCMs increase or decrease in size and increase in number over time. Hundreds of lesions may be identified, depending on the person's age and the quality and type of brain imaging used. Although CCMs have been reported in infants and children, the majority become evident between the second and fifth decades with findings such as seizures, focal neurologic deficits, nonspecific headaches, and cerebral hemorrhage. Up to 50% of individuals with FCCM remain symptom free throughout their lives. Cutaneous vascular lesions are found in 9% of those with familial cerebral cavernous malformations (FCCM; see Diagnosis/testing) and retinal vascular lesions in almost 5%.