Neurocutaneous melanosis associated with Dandy-Walker syndrome.

A young boy presented with mental retardation and seizures with extensive hairy naevi. After a fluctuating clinical course over the next 2 years, he worsened rapidly with signs of rising intracranial pressure. A CT scan revealed unsuspected features of Dandy-Walker syndrome. The clinical course is traced till the patient's death, and the implications of the coexistence of these rare conditions are discussed in view of the proposed hypotheses regarding the pathogenesis of Dandy-Walker syndrome.