Familial subacute sclerosing panencephalitis in two siblings.

Subacute sclerosing panencephalitis is a form of chronic persistent measles encephalitis in childhood which rarely manifests after wild virus infection. One previous case of familial subacute sclerosing panencephalitis in two siblings and a number of reports of subacute sclerosing panencephalitis in one member of monozygous twins have been reported in the literature. This report describes a second sibling set who both contracted subacute sclerosing panencephalitis after concurrent sporadic measles infection. Two nonimmunized brothers developed neuropsychological decline and progressive myoclonic and complex partial seizures after earlier measles infection. Stereotyped periodic 5- to 8-second complexes in the electroencephalogram suggested the diagnosis of subacute sclerosing panencephalitis, subsequently confirmed by intrathecal and serum measles-specific immunoglobulin G synthesis and the presence of rubeola nucleocapsid protein and ribonucleic acid in the biopsied brain. The viral genome has not been further subtyped in either patient at this point. Although a rare event, subacute sclerosing panencephalitis cases involving familial and singular monozygous twins may shed light on a variety of host susceptibility factors and specific viral genotype features predisposing to this disease.