SSPE uncommon noun 1. a rare chronic progressive encephalitis caused by the measles virus and occurring primarily in children and young adults; death usually occurs within three years; characterized by primary measles infection before the age of two years Synonymssubacute sclerosing panencephalitisinclusion body encephalitissubacute inclusion body encephalitissclerosing leukoencephalitissubacute sclerosing leukoencephalitisBosin's diseaseDawson's encephalitisVan Bogaert encephalitis Related words Broader terms panencephalitis WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.