Microglial nodule encephalitis: limited CNS infection despite disseminated systemic cryptococcosis.

A 28-year-old patient with AIDS was found at autopsy to have disseminated cryptococcal infection involving the lungs, spleen, lymph nodes, kidneys, gastrointestinal tract, thyroid, bone marrow, and liver. Despite widespread organ dissemination the patient did not have clinical or pathological evidence of meningitis. Microscopic examination of the brain showed cryptococci limited to the brainstem and basal ganglia; microglial nodules with multinucleate giant cells, a histological hallmark of HIV-1 encephalitis, were shown to contain Cryptococcus neoformans. This feature may suggest a form of synergism between HIV-1 and Cryptococcus neoformans. This case demonstrates an unusual form of cryptococcal neurotropism with limited CNS involvement.