Summary
Hypotrichosis simplex or hereditary hypotrichosis simplex (HHS) is characterized by reduced pilosity over the body and scalp (with sparse, thin, and short hair) in the absence of other anomalies. Prevalence is unknown but numerous large pedigrees with several affected members have been described. Both men and women are equally affected. Hair loss is diffuse and progressive and usually begins during early childhood. Body hair is also sparse with variable involvement of the eyebrows, eyelashes, and pubic and axillary hair. There are no anomalies of the skin, nails or teeth. A scalp-limited form, hypotrichosis simplex of the scalp, has also been reported (see this term). Both autosomal dominant and recessive modes of transmission have been reported for HHS. Autosomal dominant HHS affecting both scalp and body hair has been reported in only a few families and linkage to the 18p11.32-p11.23 locus has been reported in a three-generation Italian family. Three clinically similar forms of autosomal recessive HHS have recently been identified. The locus for autosomal recessive localized hereditary hypotrichosis (LAH1, involving mainly the hair of the scalp, chest arms and legs) has been mapped to 18q12.1 and mutations in the desmoglein-4 (DSG4) gene have been identified. The locus for total hypotrichosis (LAH2, characterized by sparse or absent scalp, axillary and body hair and sparse eyebrows and eyelashes) has been mapped to 3q27.3 and mutations in the lipase-H (LIPH) gene have been identified. The locus for autosomal recessive hypotrichosis simplex (LAH3, characterized by progressive loss of scalp hair, sparse body hair and normal eyebrows, eyelashes, and pubic and axillary hair) has been mapped to 13q14.11-q21.32 and mutations in a G protein-coupled receptor gene (P2RY5) have been identified. There is no treatment for hypotrichosis simplex available to date. *Author: Dr R.C. Betz (September 2009)*.
