Hypotrichosis 10

For a discussion of genetic heterogeneity of nonsyndromic hypotrichosis, see 605389.

Clinical Features

Basit et al. (2010) described a 6-generation consanguineous Pakistani family in which 5 individuals had hypotrichosis. Scalp hairs were completely absent at birth in all affected individuals. Eyebrows, eyelashes, beard, and body hairs were sparse, although in 1 affected individual beard and moustache hairs were sparse to normal. Papules were observed only on the scalp in all affected individuals. Other ectodermal structures and sebaceous and sweat glands were normal. Obligate heterozygous carriers were indistinguishable from genetically normal individuals. A scalp skin biopsy showed a markedly reduced number of hair follicles. Functional follicles produced a hair shaft which, upon reaching the skin surface, terminated with the formation of papules.

Inheritance

The pedigree pattern in the family with hypotrichosis reported by Basit et al. (2010) was consistent with autosomal recessive inheritance.

Mapping

Using linkage analysis, Basit et al. (2010) mapped hypotrichosis in a 6-generation consanguineous Pakistani family to chromosome 7p22.3-p21.3, in a 6.95-Mb region flanked by markers D7S1532 (2.49 Mb) and D7S3047 (9.44 Mb) (build 36.2). A maximum 2-point lod score of 4.74 (theta = 0) was obtained at marker D7S481 (6.09 Mb).

Molecular Genetics

Basit et al. (2010) sequenced coding exons and splice junction sites of 5 genes in the hypotrichosis critical region on chromosome 7p and failed to find any functional sequence variants. Linkage to several genes known to be involved in hypotrichosis had been excluded.