Inherited disorders of the hair.
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Congenital hair disorders may be grouped into disturbances, structural abnormalities, alopecias, and hypertrichoses. The conditions may be localized or generalized in distribution. Hair shaft abnormalities may or may not show increased fragility. The structural abnormalities may be associated to other developmental defects, in ectodermal dysplasias, and other syndromes. Alopecias are divided into those without scarring as in alopecia areata, or secondary to aplasia cutis and nevi, or due to scarring in bullous diseases such as incontinentia pigmenti and epidermolysis bullosa. Examples of hypertrichoses are lanuginosa and nevoid hypertrichosis. An overview is given on the most common inherited and congenital hair disorders with examples of some of these conditions. It is focused on the structural hair abnormalities. Different sub-types of abnormalities are demonstrated, such as pili torti, trichorrhexis nodosa, trichorrhexis invaginata and pili torti et canaliculi (Presented in the International Congress of Neonatal Dermatology, Bari, Italy, September 24-27, 1998).