The genetics of hair shaft disorders.

Many of the genes causing hair shaft defects have recently been elucidated. This continuing medical education article discusses the major types of hair shaft defects and associated syndromes and includes a review of histologic features, diagnostic modalities, and findings in the field of genetics, biochemistry, and molecular biology. Although genetic hair shaft abnormalities are uncommon in general dermatology practice, new information about genetic causes has allowed for a better understanding of the underlying pathophysiologies.