Disseminated petriellidosis (allescheriosis).

Disseminated infection by Petriellidium (Allescheria) boydii occurred in an immunosuppressed renal allograft recipient. A probable airborne pulmonary infection underwent hematogenous spread to the brain, thyroid, and heart. The organism develops septate, branching hyphae in tissue and may be misdiagnosed as Aspergillus. The basic pathologic lesions are necrosis with a predominantly polymorphonuclear leukocytic reaction and abscess formation, and a mild granulomatous response with macrophages and multinucleated giant cells. A particular tropism for blood vessels was observed. The vascular organs, brain, and thyroid have been involved in all three disseminated cases reported thus far.