Organ-specific variation in the morphology of the fungomas (fungus balls) of Pseudallescheria boydii. Development within necrotic host tissue.

Pseudallescheria boydii is an increasingly important cause of infection in debilitated and immunocompromised persons. It is frequently found within pulmonary cavities, where it forms matted collections of fungal hyphae, variously termed fungus balls, fungomas, or pseudallescheriomas. This report describes the unusual occurrence of pseudallescheriomas in the lungs, brain, and kidney. The morphological features of the fungomas varied between involved organs, with those in the lung showing well-defined layers of peripheral mycelial hypocellularity and hypercellularity consisting of anneloconidiophores and conidia. The fungomas in all organs were derived from necrotic host tissue, which resulted from nodular infarction due to fungal invasion and thrombosis of blood vessels. I believe that some previous cases of Pseudallescheria pulmonary fungomas that were ascribed to passive colonization of preformed lung cavitations may have been due to frankly invasive mycotic disease.