[Moyamoya disease in fraternal twins].

The authors have reported here fraternal twins of moyamoya disease. The one has the onset at the age of two years and six months. Then he had suffered from multiple cerebral infarction and resulting in severe neurological deficits. Now he has right hemiparesis, left homonymous hemianopsia, aphasia and mental retardation. The encephalomyo synangiosis was done to the boy bilaterally at the age of five years. The other one has the onset at the age of five years and five months. He had good physical and neurological development. The Superficial temporal artery-Middle cerebral artery anastomosis and Encephalomyo synangiosis were done bilaterally. Now his development has no problems. The twins and their younger sister all have the same HLA type. The hereditary and environmental factors may be completely related to the pathogenesis of this disease.