Some ectodermal dysplasias are here classified as congenital disorders characterized by abnormal development in 2 or more ectodermal structures (hair, nails, teeth, and sweat glands) without other systemic findings.
Witkop syndrome is a rare autosomal dominant ectodermal dysplasia involving the teeth and nails. Although a few reported cases have sparse or fine hair, almost all affected individuals have normal hair, sweat glands, and ability to tolerate heat. Affected individuals have a variable number and variable types of congenitally missing permanent and/or primary teeth, which frequently results in lip eversion due to loss of occlusion in the vertical dimension. Nails are generally thin, slow-growing, brittle, and spoon-shaped (koilonychia). Toenails are usually more severely affected than fingernails. The nail defects are alleviated with age and may not be easily detectable during adulthood (summary by Jumlongras et al., 2001). [from
OMIM]