Ectodermal Dysplasia 6, Hair/nail Type

Description

Some ectodermal dysplasias are here classified as congenital disorders characterized by abnormal development in 2 or more ectodermal structures (hair, nails, teeth, and sweat glands) without other systemic findings. Ectodermal dysplasia of the hair/nail type is a rare congenital condition characterized by hypotrichosis and nail dystrophy without nonectodermal or other ectodermal manifestations.

Clinical Features

Naeem et al. (2006) reported a consanguineous Pakistani family in which multiple members had a hair/nail form of ectodermal dysplasia. All of those affected were born with total alopecia and dystrophic nails. Hair was absent from the scalp, face, chest, arms, and legs. At 5 years of age, patients developed curly, sparse, thin hair on the scalp that could be painlessly plucked without force. Koilonychia ('spoon nails') was observed in fingernails and toenails. The toenails were thin and showed a dystrophic appearance.

Inheritance

The transmission pattern of ectodermal dysplasia in the consanguineous family reported by Naeem et al. (2006) was consistent with autosomal recessive inheritance.

Mapping

Naeem et al. (2006) genotyped 9 members (5 affected and 4 unaffected) of a consanguineous Pakistani family segregating a hair/nail type of ectodermal dysplasia using microsatellite markers in candidate regions harboring genes involved in related phenotypes. Naeem et al. (2006) mapped the disease locus to a 24.2-cM interval flanked by markers D17S839 and D17S1299 on chromosome 17p12-q21.2 (Zmax = 4.4).

Molecular Genetics

Exclusion Studies

Naeem et al. (2006) sequenced 5 epithelial keratin genes located in the candidate region on chromosome 17p12-q21.2 and did not find any pathogenic mutation in the affected individuals in a Pakistani family segregating a hair/nail type of ectodermal dysplasia.