Subacute sclerosing panencephalitis (SSPE), also known as Dawson disease, is a rare form of progressive brain inflammation caused by a persistent infection with the measles virus.

After the asymptomatic period, progressive neurological deterioration occurs, characterized by behavior change, intellectual problems, myoclonic seizures, blindness, ataxia, and eventually death.

[7][8] Symptoms progress through the following 4 stages:[9][10] A large number of nucleocapsids are produced in the neurons and the glial cells.

[11] As a result, infectious particles like the M protein are not produced, and the virus is able to survive persistently without evoking an immune response.

Faster deterioration in cases of acute fulminant SSPE leads to death within 3 months of diagnosis.

Eradication of the measles virus prevents the SSPE mutation and therefore the progression of the disease, or even the initial infection itself.