Hereditary hypotrichosis simplex: report of a family.

We report a family with hereditary hypotrichosis simplex of the scalp, a rare disorder that was first described in 1974. In our family, four out of 10 siblings were affected, including three females and one male. Examination showed thinning of the scalp hair and sparse body hair. Eyebrows, eyelashes, pubic and axillary hair were normal. Skin, nails and teeth were also normal. Hair shaft examination did not reveal any structural abnormalities. Normal follicular units, hair shafts within follicles, eccrine glands and a lack of inflammation were seen on histopathology. The primary pathology underlying this genodermatosis is unclear, but the anagen phase of the hair cycle is clearly compromised.