A 14-year-old boy develops progressive personality change, declining school performance, myoclonic jerks and periodic complexes on EEG. He had uncomplicated measles at age 3. CSF shows raised gamma globulin with oligoclonal bands and very high antimeasles antibody titres. The underlying mechanism is:

• A Immune complex deposition in cerebral vasculature after reinfection
• B Reactivation of latent measles virus from dorsal root ganglia
• C Persistence of defective, mutation-laden measles virus in CNS neurons and glia with absent M protein ✓
• D Autoimmune demyelination triggered molecularly by myelin basic protein mimicry

Explanation

Subacute sclerosing panencephalitis appears years to a decade after apparently recovered measles, caused by persistence of defective measles virus in neurons and oligodendroglia. Hypermutations in the M gene prevent assembly and release of infectious virions, producing abundant intracellular nucleocapsids, gliosis and inclusion bodies. Latency in sensory ganglia characterizes herpesviruses, not paramyxoviruses, and post-infectious demyelinating encephalomyelitis occurs days after measles rather than years later.

Reference: Nelson Textbook of Pediatrics, 22nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.