[Sibling cases of opsoclonus-polymyoclonus syndrome].

We described a 34-year-old man who developed opsoclonus-polymyoclonus syndrome (OPS) associated with benign encephalitis. His older sister also suffered from the same syndrome 12 years ago. We examined HLA types in 6 patients with OPS who were admitted to our hospital, including these sibling cases. All 6 patients have type A2 antigen and statistical analysis suggested that there is a positive relationship between OPS and HLA A2 antigen. Considering the two facts that the existence of the sibling cases in this relatively rare disorder and sharing of HLA A2 antigen in our 6 cases, some genetic factors might be involved in the development of OPS.