Moyamoya disease in a patient with hereditary spherocytosis.

Moyamoya disease (MMD) is a rare cerebral vasculopathy characterized by occlusion of the supraclinoid portion of the internal carotid artery and proximal portions of the anterior and middle cerebral arteries. Patients develop an extensive collateral network of parenchymal, transdural and leptomeningeal vessels to supply the compromised brain. These collateral channels, also known as "moyamoya vessels," may be seen in a number of disorders which lead to intracranial vascular occlusion. We report a case of MMD in a child with hereditary spherocytosis.