Hidrotic ectodermal dysplasia

Hidrotic ectodermal dysplasia, also known as Clouston syndrome, is a rare genetic disorder belonging to the group of ectodermal dysplasias — conditions that affect structures derived from the embryonic ectoderm. It is caused by mutations in the GJB6 gene, which encodes connexin 30, a gap junction protein important for cell-to-cell communication in the skin and its appendages. Unlike other forms of ectodermal dysplasia, hidrotic ectodermal dysplasia notably preserves sweat gland function (hence the term 'hidrotic,' meaning sweating is intact), while primarily affecting the hair, nails, and skin. The hallmark clinical features include severe nail dystrophy (thickened, slow-growing, discolored, or absent nails), sparse to absent scalp hair (hypotrichosis or alopecia that may be progressive), and sparse or absent body hair including eyebrows and eyelashes. The nails are often the most consistently affected feature and may be present from birth or early childhood. Palmoplantar hyperkeratosis — thickening of the skin on the palms and soles — is another common finding. Teeth and sweat glands are typically normal, which distinguishes this condition from hypohidrotic forms of ectodermal dysplasia. Some affected individuals may also develop hyperpigmentation of the skin, particularly over the joints. There is currently no cure for hidrotic ectodermal dysplasia. Treatment is symptomatic and supportive, focusing on management of nail abnormalities, skin care for hyperkeratotic areas, and cosmetic solutions such as wigs for hair loss. Dermatologic follow-up is recommended. Genetic counseling is important for affected families given the autosomal dominant inheritance pattern. The condition was originally described in a large French-Canadian kindred, and notable clusters have been reported in this population, though cases occur worldwide across various ethnic groups.

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