Critical Review of Human Isolates of Wangiella dermatitidis

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Abstract
Isolates (26) that had been called W. dermatitidis (including Kano''s type culture) and were variously described in the literature as causal agents of chromoblastomycosis, chromomycosis or phaeohyphomycosis were studied critically. Of the 26, 21 proved to be W. dermatitidis on the basis of colonial and microscopic morphology, thermotolerance, decomposition of tyrosine and exoantigen tests. Of the 21 confirmed isolates, 18 were from Japan, 2 from Taiwan and 1 from the USA. The remaining 5 isolates were identified as Exophiala jeanselmei (2), E. moniliae (2) and Fonsecaea pedrosoi (1). The clinical aspects of the infections, their treatment and the histopathologic appearance of the etiologic agents were reviewed in 21 cases of phaeohyphomycosis. W. dermatitidis should be recognized as a dermatotropic and a neurotropic agent among the pathogenic dermatiaceous Hyphomycetes. The high case-fatality rate (48%) caused by W. dermatitidis clearly emphasizes that this mold is an important agent of systemic phaeohyphomycosis with a marked tendency to invade the CNS. 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, alone or in various combinations. The absence of muriform cells clearly showed that the patients had developed phaeohyphomycosis, not chromoblastomycosis. The ambiguous and inappropriate term sclerotic cells should be replaced by the more appropriate term muriform cells to describe precisely the tissue form of the causal agents of chromoblastomycosis.