Subacute sclerosing panencephalitis in one member of identical twins.

Two identical twins contracted measles simultaneously in the same house at the age of six months. Only one member developed subacute sclerosing panencephalitis (SSPE) at the age of ten years. The other member remained healthy until after two years of follow-up. This case emphasizes the importance of factors other than host-measles virus interaction in the pathogenesis of SSPE.