A 14-year-old boy presents with progressive myoclonus, intellectual decline, and generalized seizures over eight months. EEG shows periodic complexes and CSF anti-measles antibodies are elevated. He had uncomplicated measles at age three. The underlying pathogenesis involves:

• A Reinfection of neurons by wild-type measles virus acquired from a contact
• B Persistent CNS infection with defective measles virus carrying mutations in the M (matrix) protein, with defective budding ✓
• C Immune-complex deposition in cerebral vasculature following vaccination
• D Latent measles virus in dorsal root ganglia reactivating under immunosuppression

Explanation

Subacute sclerosing panencephalitis (SSPE) emerges years after apparent recovery from measles, caused by persistent central nervous system infection with mutant measles virus. Mutations in the M (matrix) protein gene impair virion assembly and budding, allowing the virus to persist intracellularly and spread cell to cell while evading humoral clearance, yet antibody titres in serum and CSF remain strikingly high. Measles does not establish ganglionic latency like herpesviruses, and SSPE is not a reinfection event.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.