A 16-year-old boy presents with slowly progressive intellectual deterioration and generalized myoclonic jerks. EEG shows periodic complexes. He had measles at 14 months of age and was never vaccinated. CSF measles antibody titers are markedly elevated. The pathogenesis of his condition involves:
- A Reinfection with wild-type measles virus producing recurrent encephalitis
- B Autoimmune demyelination cross-reacting with myelin basic protein after measles vaccination
- C Persistent CNS infection with defective measles virus lacking functional matrix protein, allowing evasion of immune clearance ✓
- D Latent measles virus in sensory ganglia reactivating during adolescence
Correct answer: C. Persistent CNS infection with defective measles virus lacking functional matrix protein, allowing evasion of immune clearance
Explanation
Subacute sclerosing panencephalitis appears years after uncomplicated measles and results from persistent CNS infection with a defective measles virus, typically with mutations in the matrix (M) gene that block virion assembly and budding. The altered virus spreads neuron to neuron and evades humoral immunity, though high anti-measles antibody levels persist in serum and CSF. It follows primary infection, not reinfection or ganglionic latency.
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.