A 15-year-old boy presents over two years with declining school performance, myoclonic jerks, and personality change progressing to dementia. EEG shows periodic complexes and CSF measles antibody titers are markedly elevated. He had measles at age 4 and was unvaccinated. The pathogenesis of this late complication involves:
- A Defective expression of the measles matrix (M) protein allowing persistent CNS infection with mutant virus ✓
- B Immune-complex deposition in cerebral vessels following repeated reinfections
- C Reactivation of latent virus from dorsal root ganglia after immunosuppression
- D Autoimmune demyelination triggered by molecular mimicry with peripheral nerve antigens
Correct answer: A. Defective expression of the measles matrix (M) protein allowing persistent CNS infection with mutant virus
Explanation
Subacute sclerosing panencephalitis appears 5 to 10 years after measles, caused by defective measles virus persisting in neurons and glia. Mutations, especially affecting the matrix (M) protein, prevent assembly and release of mature virions while allowing intracellular spread, evading antibody clearance. High CSF measles antibody supports the diagnosis. Distractor C misattributes latency to ganglia, a property of herpesviruses, and D describes post-infectious encephalomyelitis, an earlier and demyelinating entity.
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.