Hereditary congenital :hypotrichosis is an autosomal dominant pilar dysplas
ia first described by Marie Unna in an extended German family. The diffuse
hair defect typically occurs as an isolated phenomenon and the ultrastructu
ral hair findings consist of-both torsion and longitudinal grooving of the
hair shaft. A large pedigree comprising 6 generations with 20 members affec
ted by Marie Unna hypotrichosis from Italy is reported.