Monilethrix: a rare hereditary condition.

Monilethrix is a rare hereditary condition generally considered to be an autosomal-dominant disorder with variable penetrance. Here, we report a case of monilethrix in a 13-year-old boy with an affected sibling. A therapeutic trial with oral N-acetyl cysteine was attempted. There was slight improvement after 2 months of therapy. The hair density, however, did not show any further improvement subsequently. Monilethrix remains as a therapeutic challenge for dermatologists.