Clinical features of moyamoya disease in sibling relations under 15 years of age.

This study was undertaken to define the clinical features of moyamoya disease in sibling relations less than 15 years of age. We analysed five pairs of siblings (6 boys, 4 girls) with moyamoya disease from among 56 moyamoya patients less than 15 years of age. Of 56 paediatric patients with moyamoya disease, 5 were sibling pairs. At onset of the disease, all patients were under 10 years of age. Clinical manifestations in the proband and the affected sibling tended to present as transient ischaemic attacks; none of the 10 patients presented with intracranical haemorrhage. The probands were not always the older sibling, however, the time lapse between disease onset in the proband and his/her sibling was less than one year. Among the sibling pairs, there was no striking difference in disease staging based on angiographic findings. The incidence of sibling occurrence of moyamoya disease appears to be higher than previously assumed and the family of children with moyamoya disease should be cautioned that their other children have an increased risk of developing the illness.