Critical review of human isolates of Wangiella dermatitidis

We studied critically 26 isolates that had been called Wangiella dermatitidis (including Kano's type culture) and were variously described in the literature as causal agents of chromoblastomycosis, chromomycosis, or phaeohyphomycosis. Only 21 of the 26 proved to be W. dermatitidis, on the basis of colonial and microscopic morphology, thermotolerance, decomposition of tyrosine, and exoantigen tests. Eighteen of the 21 confirmed isolates were from Japan, two from Taiwan, and one from the U.S. The remaining five isolates were identified as Exophiala jeanselmei (2), E. moniliae (2), and Fonsecaea pedrosoi (1). We also reviewed the clinical aspects of the infections, their treatment, and the histopathologic appearance of the etiologic agents in 21 cases of phaeohyphomycosis. Wangiella dermatitidis should be recognized as a dermatotropic as well as a neurotropic agent among the pathogenic dematiaceous Hyphomycetes. The high case-fatality rate (48%) caused by W. dermatitidis clearly emphasizes that this mould is an important agent of systemic phaeohyphomycosis with a marked tendency to invade the central nervous system. In the case reports, the indiscriminate use of the term "sclerotic cells" to describe the tissue forms of these fungi was not in accord with their true nature. In tissue they developed dark-walled mycelium, spherical cells, with or without buds or toruloid hyphae, either alone or in various combinations. The absence of muriform cells clearly showed that the patients had developed phaeohyphomycosis, not chromoblastomycosis. We propose that the ambiguous and inappropriate term "sclerotic cells" be replaced by the more appropriate term "muriform cells" to describe precisely the tissue form of the causal agents of chromoblastomycosis.