We present familial Moyamoya disease in two European children and emphasize the 
importance of familial factors in the pathogenesis of this disease and its 
appearance not only in Asians but in the Western population as well. The first 
patient, a Greek female infant, also has coagulation disorders. Her mother, also 
suffering from Moyamoya and other family members, have similar coagulation 
disorders (Factor V Leiden, Methylene-tetrahydrofolic reductase and Factor II 
20210A mutations). The second patient, a Scottish boy, is unique in that 
familial Moyamoya affects five members of three consecutive generations of his 
maternal family. Genetic analysis in the Greek family demonstrated no 
abnormality on chromosome 3p26, as in other cases. However, the mitochondrial 
DNA and Y chromosomal genotype showed that affected members had the same 
sequence of the Mitochondrial 3 portion of D-loop with Japanese patients. These 
findings suggest that the pathogenesis of Moyamoya may vary across races and 
ethnic groups.