Hereditary Trichodysplasia: Marie Unna'S Hypotrichosis

This is a study of eight members of one family with Marie Unna hypotrichosis occurring in five generations. All affected individuals were born with widespread facial “milia”, sparse scalp hair and decreased body hair. Laboratory studies including urinary amino acids and plasma testosterone were normal. On histologic examination the hair follicles of the scalp showed proliferation of the internal root sheath and horn pearl formation in the lower third of the follicle. Abnormal hairs were flat and ribbon-like and twisted at irregular intervals. Extensive peeling of the cuticle was demonstrated by scanning electron microscopy. Electron microscopy of the hair shafts revealed intracellular fractures of the cuticular cells, increased interfibrillar matrix and fractures of the cortical cell fibrils and fractures of the medullary cells. X-ray diffraction studies were normal. On amino acid analysis of affected hairs a small decrease in cysteine-cystine and an increase in methionine content was noted. Since the hair shafts are clearly abnormal in this disorder, the name hereditary trichodysplasia is suggested. The condition is inherited as an autosomal dominant trait