Human Brain Bank, NIMHANS, Bangalore 61

Viral Infections

CASE 23: HIV ENCEPHALITIS (HIV -1): (Slide 23: H&E)

HIstology:The section through the cerebral cortex showed leptomeninges with minimal inflammatory

component. In the grey matter, focal aggregates of microglial cells are seen with minimal or sparse lymphocytic component. Occasional, small multinucleated giant cells are seen in the midst of neurons. The neurons are fairly well preserved with distinct nucleus and nucleolus. Astrocytosis is not evident. In the subcortical white matter, in the vicinity of blood vessels small microglial aggregates are seen along with a rare small giant cell with glassy eosinophilic cytoplasm. In the perivascular space histiocytes with brownish hemosiderin and lymphocytes are seen. No distinct vascular pathology is evident. The white matter showed patchy demyelination. The microglial cells and giant cells are labeled by p24 antigen of HIV establishing the diagnosis of HIV encephalitis – (as both grey and white matter show the pathology)

dIagnosIs: HIV ENCEPHALITIS

comment: HIV encephalitis was initially described as subacute or microglial nodule encephalitis associated

with HIV, similar to a few other viral encephalitidis. The presence of small multinucleated giant cells (MNGCS), with abundant eosinophilic cytoplasm and peripherally arranged hyperchromatic multiple convoluted nuclei, is haracteristic of HIV encephalitis. The microglial cells and the giant cells contain variable amount of p24 HIV viral protein. The presence of giant cells with microglial response is not consistent and may not be found at all or needs extensive sampling and diligent search. The pathology is more frequent in subcortical white matter and basal ganglia. The giant cells may be found widely scattered, singly in the parenchyma, away from the microglial cells and other inflammatory component. These giant cells are reported more frequently in pediatric AIDS than in adult cases. The HIV encephalitis is usually found to be associated clinically with AIDS Dementia Complex (ADC) with or without multinucleated giant cell response, but only one fourth of cases of ADC have demonstrable HIV encephalitis. HIV leucoencephalopathy, also a pathological entity associated with HIV, show a triad of pathology, myelin reduction, reactive astrogliosis, microglial and lympho-histiocytic reaction with multinucleated giant cells (MNGC), involving the deep white matter of the cerebral hemispheres with relative symmetry. The blood vessels show thickening of the wall and endothelial prominence. Some of the microvessels may show extravasation of fibrin, reflecting alteration in blood-brain-barrier following HIV infection.

62 National Institute of Mental Health and Neuro Sciences

Common Infections of the Nervous System

CASE 23 - HIV ENCEPHALITIS

Fig A: Cerebral cortex shows a cluster of microglial cells along with small giant cells, in the midst of neurons. There is no astrocytosis and the neurons are fairly well preserved. (H&E Obj X 20)

Fig B & C: The white matter has aggregates (Fig B) of microglial cells and multiple small multinucleated giant cells (arrow) (Fig C). The giant cells contain p24 antigen of HIV (B, inset) Lymphocytic response is minimal. The white matter in these areas shows patchy demyelination

(B: Obj X 20, B, inset: IHC (p24) Obj X 40, C: H&E Obj X 40)