Given the discrepancy between autopsy data and clinically reported data, we suspect that the incidence of GIH is underestimated and clinicians should consider this diagnosis in AIDS patients at risk, specifically those with advanced immunosuppression (i.e., CD4+ cell counts <100 cells/mm3) who reside in endemic areas (Ohio or Mississippi river valleys as well as temperate regions of Central and South America, Africa, and Asia) and/or have a prior history of histoplasmosis. This evidence concerns the gene CD4 and histoplasmosis.