Monilethrix: a review and case report.

tion meaning necklace hair, is a rare ectoder.mal condition inherited as an autosomal dominant trait with high penetrance and variable expressivity.1.2 The latter characteristic may be partially due to hormonal fluctuations, including puberty and pregnancy, and to environmental factors such as seasonal changes.2 The degree of expressivity is difficult to quantitate. 2 Some patients are so mildly affected that their hair disorder is overlooked.3 However, very mild and quite severe cases of monilethrix have been found within the same sibship. 2 Both males and females are equally affected, and expressivity seems to be equally variable within families. Individuals affected with rare autosomal disorders have one affected parent and the condition is transmitted for generations. Fifty percent of the children will have the condition as a result of one affected parent and one unaffected parent. 4 Not every case has affected parents; new mutations are possible. The incidence is unknown. Most known cases are of European origin, however, Indian and Arab pedigrees have been described, s Extensively affected kindreds with the pattern of dominant inheritance have been reported, s Solomon and Schnyder in McKusick5 suggested that one of five families might have a recessive form of the disorder. This condition is characterized by a variation in the hair shaft thickness, with small node-like deformities that produce a beaded appearance, internodal fragility, breakage, and partial alopecia. 6 Alopecia may be the presenting manifestation, s The degree of alopecia varies from patient to patient and from time to time in the same individual, s In this disorder, normal neonatal lanugo hairs are shed during the first week of life, and subsequent hair growth -generally at about the second month of life -becomes dry, lusterless, and brittle, failing to grow to any appreciable length. 6 Affected hairs are short, usually < 1.9 cm in length, but some patients have longer hair (reaching almost 7 cm). 1