Rapidly progressive subacute sclerosing panencephalitis: an ultrastructural and immunoperoxidase study.

A case of subacute sclerosing panencephalitis (SSPE) in a 20-year-old male who died within 2 months, is described. Light microscopy revealed massive neuronal loss, reactive gliosis, perivascular cuffing and intranuclear (Cowdry type A) and intracytoplasmic inclusions. Immunocytochemical stain with the complement-fixing measles antibody was positive for intranuclear and intracytoplasmic inclusions. The reactive glia cells were positive for glial fibrillary acidic protein. Electron microscopy revealed a paramyxovirus-like structure of the nucleocapsids, occasionally showing a 'fuzzy' appearance in the cytoplasm. Crystal-like intracytoplasmic inclusions were also seen. The inclusions occurred in oligodendroglia cells, astrocytes and neurons. This case illustrates a rapidly progressive form of SSPE which, in some aspects, differs from the chronic form and resembles acute measles encephalitis.