A 35-year-old man with HIV (CD4 count 40 cells/μL) develops rapidly progressive dementia, aphasia, and visual field defects. MRI shows multiple non-enhancing white matter lesions without mass effect. CSF PCR detects JC virus. What is the condition, and what is the pathological mechanism of demyelination?
- A CNS toxoplasmosis — necrosis of neurons by intracellular Toxoplasma tachyzoites
- B Progressive multifocal leukoencephalopathy (PML) — JC virus-mediated lytic infection and destruction of oligodendrocytes ✓
- C CMV encephalitis — cytomegalic cells destroying ependyma and periventricular white matter
- D HIV encephalitis — microglial nodules and multinucleated giant cells destroying cortical neurons
Explanation
Progressive multifocal leukoencephalopathy (PML) is caused by reactivation of latent JC polyomavirus in severely immunocompromised patients (CD4 <200/μL). JC virus infects and lyses oligodendrocytes, which are responsible for myelin maintenance in the CNS; destruction of oligodendrocytes causes large irregular demyelinating lesions in white matter. Histology shows enlarged, atypical oligodendrocyte nuclei with intranuclear viral inclusions and bizarre astrocytes. CNS toxoplasmosis produces ring-enhancing lesions; CMV encephalitis causes periventricular enhancement; HIV encephalitis causes subcortical dementia without large white matter lesions.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.