Comparative histopathology of Dactylaria constricta, Fonsecaea pedrosoi, Wangiella dermatitidis, and Xylohypha bantiana in experimental phaeohyphomycosis of the central nervous system.

Summary: The comparative neuropathology of experimental phaeohyphomycosis due to Dactylaria constricta (D. gallopava; Scolecobasidium constrictum), Fonsecaea pedrosoi, Wangiella dermatitidis (Exophiala dermatitidis), and Xylohypha bantiana cladosporium bantianum; C. trichoides), was studied in the mouse central nervous system (CNS). All fungi appeared as brown hyphae on hematoxylin and eosin stain. Zigzag forms of hyphae were common in all species except F. pedrosoi. Neither blastoconidia nor chlamydoconidia were present in tissue infected with D. constricta. D. constricta, W. dermatitidis, and X. bantiana were distributed hematogenously throughout the cerebral hemispheres and demonstrated intraluminal, microvascular invasion whereas, CNS infection due to F. pedrosoi developed by extension from extracerebral dural lesions. F. pedrosoi invaded small to medium‐sized cerebral arteries and veins by extraluminal extension. Microabscesses and early granuloma formation occurred with D. constricta, W. dermatitidis, and X. bantiana, but not with F. pedrosoi, which was associated with only scant cellular inflammatory reaction. Only D. constricta caused a necrotizing ventriculitis with periventricular hemorrhage. Other than yeast‐like cells in W. dermatitidis and F. pedrosoi, ventriculitis in D. constricta, and epidural invasion in F. pedrosoi, these infections are remarkably similar in tissue.