Marie-Unna hereditary hypotrichosis: case report and review of the literature.

We present an 18-year-old girl with progressively worsening hair thinning and loss since puberty. Her clinical history, physical examination, and pathology results were consistent with Marie-Unna hereditary hypotrichosis, a rare cause of autosomal dominant hereditary hair loss. She had no family history of similar hair loss and represents the first report of a new case of Marie-Unna hereditary hypotrichosis within a previously unaffected family.