Definition of Subacute sclerosing panencephalitis:

Subacute sclerosing panencephalitis (SSPE) is a progressive, debilitating, and fatal brain disorder caused by infection with a mutant measles (rubeola) virus. A mutant virus is one that has undergone genetic changes (mutations).

Causes, incidence, and risk factors:

Ordinarily, the measles virus does not cause brain damage, but certain mutant forms may invade the brain, causing severe illness and death. SSPE has been reported in all parts of the world, but in western countries it is considered a rare disease.

Fewer than 10 cases per year are reported in the United States, a dramatic decrease that followed the nationwide measles immunization program. However, in some countries like India, over 20 cases of SSPE per million people are reported each year.

SSPE tends to occur several years after an individual has measles, even though the person seems to have fully recovered from the illness. Males are more often affected than females, and the disease generally occurs in children and adolescents.

Affected individuals frequently die 1 to 2 years after being diagnosed with this condition, but some may survive for longer periods.

SSPE is due to the direct invasion of brain cells by the mutant measles virus, which provokes brain inflammation (swelling and irritation) that may last for years.