Moyamoya disease is a cerebrovascular disorder of unknown etiology. Its high 
incidence in East Asia and accumulation in family members suggest a genetic 
background. A high incidence of maternal inheritance implicates genomic 
imprinting in this disorder. Based on this hypothesis, we studied the 
association between moyamoya disease and IGF2R gene on chromosome 6, but found 
no evidence for such association between them. On the other hand, heterogeneous 
expressions of IGF2R were confirmed in the lymphocytes. Some individuals showed 
monoallelic expression and others showed biallelic expression.