Mucopolysaccharidosis type IIIA, or Sanfilippo syndrome type A, is a lysosomal storage disorder caused by deficiency of heparan N-sulfamidase, resulting in defective degradation and subsequent storage of heparan sulfate. It is characterized by progressive nervous system involvement. Cribriform changes in the corpus callosum, basal ganglia, and white matter, diffuse high-intensity signal in the white matter, and cerebral atrophy have been described in patients with this disorder. This case report describes a child with Sanfilippo syndrome type A who exhibited fairly mild clinical findings but-an unusual magnetic resonance imaging pattern that included multiple moderate-sized cysts (probably enlarged perivascular spaces) within the corpus callosum and an abnormal appearance of the clivus and cervical vertebrae. This case calls attention to the variety of appearances possible with magnetic resonance imaging in Sanfilippo syndrome type A. (C) 2008 by Elsevier Inc. All rights reserved.