Sanfilippo's syndrome type C--the first known case in South Africa.

The clinical, radiological and biochemical findings in a black girl with a rare, inherited mucopolysaccharide storage disease, Sanfilippo's syndrome (mucopolysaccharidosis (MPS) III) type C, are described. Practical points concerning the biochemical diagnosis of this condition, arising from unusual characteristics of the deficient enzyme acetyl CoA: alpha-glucosaminide N-acetyltransferase, are discussed. Because phenotypic manifestations of mucopolysaccharidosis are mild in all four types of Sanfilippo's syndrome and screening tests for mucopolysacchariduria in these patients may be negative, many cases may be passed unrecognized or simply labelled as cases of nonspecific mental retardation. It is suggested that Sanfilippo's syndrome is grossly underdiagnosed in the RSA and clinicians are urged to develop a greater awareness of the existence, and often subtle presentation, of the condition.