Subacute sclerosing pan encephalitis (SSPE): Persistent measles Virus infection

Subacute sclerosing pan encephalitis (SSPE), also called Dawson’s encephalitis, is a persistent measles infection of the central nervous system. SSPE is a progressive, fatal, encephalopathy characterized by personality changes, mental deterioration, involuntary movements, muscular rigidity, and death. SSPE usually begins 4–10 years after the patient has recovered from naturally acquired measles.
Successful isolation of measles virus from brain and lymphoid tissues of SSPE patients clearly established measles virus as the etiologic agent of the disease. Molecular characterization of measles virus nucleic acid sequences derived from brain biopsy or autopsy has identified wild-type measles sequences with few exceptions, and not those of the vaccine strains.
Measles virus genotypes found in association with SSPE clinical specimens are generally the circulating sequences, in the geographic region where the patients acquired natural infection. No vaccine sequences were identified from tissues of SSPE patients.
SSPE is a very rare but lethal disease, persisting in the human central nervous system (CNS). It is characterized by the absence of viral budding, reduced expression of the viral envelope proteins and spread through the CNS despite massive immune responses. The persistence of measles virus in the brain cells may be due to mutations in the MV genes that were introduced not only due to errors of the MV polymerase, but also in clusters due to hypermutations. The other reasons may be the MV matrix (M) gene, which is most heavily mutated, mutation in the transmembrane glycoproteins, which may be the cause of genetic defects in the persisting measles virus.
The diagnosis is clinical and immunological evidence of measles infection. Management of the disease includes seizure control and avoidance of secondary complications associated with the progressive disability.
Treatment with interferon, ribavirin, and Isoprinosine have reported to give beneficial results. However, the disease shows continuous progression; only 5% of individuals with SSPE undergo spontaneous progress, with the remaining 95% dying within 5 years of diagnosis.