Diagnosis:
Clinical and imaging features plus laboratory findings
Clinical features:
Gradual onset & progressive. Seizures & aphasia may occur
Occurs in the setting of immunosupression: e.g. HIV infection/AIDS, immunosupressant medications,
Findings on Investigations:
JC virus in CSF: by PCR
MRI:
- White matter lesions, usually asymmetric but bilateral, periventricular and subcortical involvement of U fibres, spares cortex, confluent, usually parieto-occipital, may involve corpus callosum, don’t conform to cerebral territories, lesions may extend from the white matter to the deep grey matter
- No edema, no mass effect or enhancement
- T2: increased signal
- T1: decreased signal
- T1+gadolinium: no enhancement
CT:
- Hypodense white matter lesions
Pathology, brain biopsy:
Demyelination: macrophages with myelin
JC oligodendrocytes with intranuclear inclusions (enlarge amphophilic nuclei)
Astrocytic gliosis with bizarre astrocytes
No inflammatory infiltrate unless associated with immune reconstitution syndrome where there are lymphocytes
Special studies:
- Immunohistochemistry for polyomavirus: positive
- In situ hybridization ISH for JCV DNA
Treatment:
Treat the underlying cause of immunosuppression