Quasi-moyamoya disease and heterozygosity for homocystinuria in a five-year-old girl.

We report a patient with quasi-Moyamoya disease who presented with acute left hemiparesis. Routine metabolic evaluation was normal. However, by performing a methionine loading test and measurement of cystathionine synthase activity in cultured fibroblasts the diagnosis of heterozygosity for homocystinuria (HC) was established. Only recently it has been shown that heterozygosity for HC is a risk factor for premature cerebrovascular disease in adults. The present case suggests that also in children with cerebrovascular disorders the analysis of its pathogenesis should include extensive metabolic studies on homocysteine metabolism.