marie unna hereditary hypotrichosis marie unna hereditary hypotrichosis marie unna hereditary hypotrichosis is an autosomal dominant condition characterized by scalp hair that is sparse or absent at birth, with variable coarse, wiry hair regrowth in childhood, and potential loss again at puberty.: 639 marie unna hereditary hypotrichosisother namesmarie unna hypotrichosisspecialtymedical genetics