Menkès syndrome is a sex-linked recessive disease. The authors previously reported a case in a boy whose neurologic condition deteriorated gradually until death occurred at the age of seven and a half months. Diagnosis was confirmed by the finding of very low plasma levels of copper and ceruloplasmin. Evaluation of family members disclosed hypopigmentation of one half of the abdomen in three sisters and in the carrier mother. This hypopigmentation may be ascribed to decreased melanocyte copper-dependant tyrosinase activity. Among cells in the body, this anomaly may be present or absent according to whether or not the abnormal X chromosome is inactivated.