Cryptococcosis of the lung in a patient with AIDS, mucicarmine stain. This micrograph shows the widened alveolar septum containing a few inflammatory cells and numerous yeasts of Cryptococcus neoformans. The inner layer of the yeast capsule stains red. Cryptococcosis is a rare infection and affects people with a deficient immune system such as in AIDS cases. It is caused by inhaling fungus spores found in soil contaminated by pigeon droppings. Infection may cause meningitis or granular growths in the lungs, skin or elsewhere.