Clouston's hidrotic ectodermal dysplasia
Encyclopedia
Clouston's hidrotic ectodermal dysplasia (also known as "Alopecia congenita with keratosis palmoplantaris," "Clouston syndrome," "Fischer–Jacobsen–Clouston syndrome," "Hidrotic ectodermal dysplasia," "Keratosis palmaris with drumstick fingers," and "Palmoplantar keratoderma and clubbing") is caused by mutations in a connexin
gene, GJB6 or connexin-30, characterized by scalp hair that is wiry, brittle, and pale, often associated with patchy alopecia
.
Disease characteristics. Hidrotic ectodermal dysplasia 2, or Clouston syndrome (referred to as HED2 throughout this entry) is characterized by partial or total alopecia, dystrophy of the nails, hyperpigmentation of the skin (especially over the joints), and clubbing of the fingers. Sparse scalp hair and dysplastic nails are seen early in life. In infancy, scalp hair is wiry, brittle, patchy, and pale; progressive hair loss may lead to total alopecia by puberty. The nails may be milky white in early childhood; they gradually become dystrophic, thick, and distally separated from the nail bed. Palmoplantar keratoderma may develop during childhood and increases in severity with age. The clinical manifestations are highly variable even within the same family.
Diagnosis/testing. HED2 is suspected after infancy on the basis of physical features in most affected individuals. GJB6 is the only gene known to be associated with HED2. Targeted mutation analysis for the four most common GJB6 mutations is available on a clinical basis and detects mutations in approximately 100% of affected individuals. Sequence analysis is also available on a clinical basis for those in whom none of the four known mutations is identified.
Management. Treatment of manifestations: special hair care products to help manage dry and sparse hair; wigs; artificial nails; emollients to relieve palmoplantar hyperkeratosis.
Genetic counseling. HED2 is inherited in an autosomal dominant manner. Most individuals with HED2 have an affected parent; de novo gene mutations have also been reported. Offspring of affected individuals have a 50% chance of inheriting the mutation and being affected. Prenatal testing for pregnancies at increased risk is possible if the disease-causing mutation in an affected family member is known; however, requests for prenatal testing for conditions such as HED2 are not common.
Connexin
Connexins, or gap junction proteins, are a family of structurally-related transmembrane proteins that assemble to form vertebrate gap junctions . Each gap junction is composed of two hemichannels, or connexons, which are themselves each constructed out of six connexin molecules...
gene, GJB6 or connexin-30, characterized by scalp hair that is wiry, brittle, and pale, often associated with patchy alopecia
Alopecia
Alopecia means loss of hair from the head or body. Alopecia can mean baldness, a term generally reserved for pattern alopecia or androgenic alopecia. Compulsive pulling of hair can also produce hair loss. Hairstyling routines such as tight ponytails or braids may induce Traction alopecia. Both...
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See also
- Palmoplantar keratodermaPalmoplantar keratodermaPalmoplantar keratodermas are a heterogeneous group of disorders characterized by abnormal thickening of the palms and soleAutosomal recessive and dominant, X-linked, and acquired forms have all been described.There are also acquired forms of the condition....
- List of cutaneous conditions
Disease characteristics. Hidrotic ectodermal dysplasia 2, or Clouston syndrome (referred to as HED2 throughout this entry) is characterized by partial or total alopecia, dystrophy of the nails, hyperpigmentation of the skin (especially over the joints), and clubbing of the fingers. Sparse scalp hair and dysplastic nails are seen early in life. In infancy, scalp hair is wiry, brittle, patchy, and pale; progressive hair loss may lead to total alopecia by puberty. The nails may be milky white in early childhood; they gradually become dystrophic, thick, and distally separated from the nail bed. Palmoplantar keratoderma may develop during childhood and increases in severity with age. The clinical manifestations are highly variable even within the same family.
Diagnosis/testing. HED2 is suspected after infancy on the basis of physical features in most affected individuals. GJB6 is the only gene known to be associated with HED2. Targeted mutation analysis for the four most common GJB6 mutations is available on a clinical basis and detects mutations in approximately 100% of affected individuals. Sequence analysis is also available on a clinical basis for those in whom none of the four known mutations is identified.
Management. Treatment of manifestations: special hair care products to help manage dry and sparse hair; wigs; artificial nails; emollients to relieve palmoplantar hyperkeratosis.
Genetic counseling. HED2 is inherited in an autosomal dominant manner. Most individuals with HED2 have an affected parent; de novo gene mutations have also been reported. Offspring of affected individuals have a 50% chance of inheriting the mutation and being affected. Prenatal testing for pregnancies at increased risk is possible if the disease-causing mutation in an affected family member is known; however, requests for prenatal testing for conditions such as HED2 are not common.