ABSTRACT
The ascomycete order Onygenales is important from the medical perspective because it includes the sexual stages of the true fungal pathogens of humans and animals (i.e., the dermatophytes and the dimorphic fungi capable of causing disease in an otherwise healthy host). The Onygenales includes three families: the Arthrodermataceae, including dermatophytes (treated in this volume, Chap. 5); the Onygenaceae, including the dimorphic fungi; and the Gymnoascaceae. Although a prior version of this volume (1) treated the Onygenaceae as part of the Eurotiales, the most recent treatment of the ascomycetes (2) maintains it within the order Onygenales separately from the Eurotiales. This chapter describes the pathogenic members of the Onygenaceae as well as some nonpathogenic species that may resemble them and that are rare to common contaminants in clinical specimens. A few members of the Gymnoascaceae are also treated. A fourth family, the Myxotrichaceae, formerly included within the Onygenales (3, 4), appears instead to have affinities to the inoperculate discomycetes (5). Notwith-standing its probable disparate relationship to onygenalean fungi, some members of the Myxotrichaceae are included here for convenience.
