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Monilethrix is an autosomal dominant hair shaft dysplasia. This rare genodermatosis is characterized by periodic constrictions of the hair shaft giving the appearance of beaded hair. It is accompanied by fragility, local follicular hyperkeratosis and pronounced hypotrichosis. Patients may also present with nail dystrophy. Examination of this hair under light microscopy shows the periodic alternation of constrictions (defect) and nodes (real hair diameter). Electron microscopy reveals that the hair has broken off at the constriction areas. Monilethrix is due to a mutation in the type II keratin genes: hHb1 and hHb6. Treatment consists in topical retinoic and glycolic acid or minoxidil in postpuberal patients, although this condition improves over the years. |