A two year old developmentally delayed girl with neurofibromatosis type I and a sudden onset of left sided hemiparesis is reported from the Children’s National Medical Center and George Washington University School of Medicine, Washington, D.C. There was no history of sickle cell disease or hypertension. The hemiparesis gradually improved and the patient received aspirin, 80 mg. daily. Four months later there was a left focal seizure and an acute progression of the left hemiparesis. At 5 years of age the patient presented with sudden right-sided weakness and right focal seizure. Cerebral angiography revealed bilateral distal internal carotid arterial occlusion. 
COMMENT. Moyamoya may be seen in association with a number of systemic conditions including NF-1 or as a distinct disease entity of unclear etiology. Occlusion of the intracranial arteries is a rare complication of NF-1 and the progressive occlusion noted in this case appears to be unique.
The gene for NF-1 has been mapped to chromosome 17 and closely linked DNA markers have made accurate diagnosis by linkage analysis possible in most cases of familial NF-1. DNA testing by linkage analysis on 24 individuals with a family history of NF-1 and on 9 couples who requested testing for prenatal diagnosis was found useful as an adjunct to the clinical diagnosis 1) in children less than 6 years of age with incomplete clinical signs, 2) in NF-1 families for prenatal testing, and 3) when complete clinical examination is impracticle.