The analysis of genetically determined hair defects

A classification of genetically determined hair defects based on pathophysiologic considerations is presented to facilitate research in this area. The categories in the classification are: 1) hair with periodic defects in structure; 2) complete or partial failure of hair development manifested by sparseness; 3) hairs with structural protein abnormalities and 4) defective hairs associated with metabolic defects. The methodologies for the study of hair are discussed including a new technic to directly measure Young's modulus of elasticity. A new autosomally dominantly inherited disorder with sparse hair and milia is presented.