[Pityriasis versicolor and the yeasts of genus Malassezia].

Although pityriasis versicolor is the only human disease for which Malassezia yeasts have been fully established as pathogens, it is still not clear which species are implicated. Most studies carried out in recent years support our hypothesis - proposed in 1999 - that Malassezia globosa is the predominant species in pityriasis versicolor lesions, at least in temperate climates. Confirmation of this hypothesis could help us understand the conditions, as yet unclear, that induce transformation of this yeast from the saprophytic form present in healthy skin to the parasitic form, characterized by the formation of pseudomycelium, and could also guide therapy. In addition, isolation of another species, Malassezia furfur, which seems to be predominant in the tropics, raises the possibility of a second etiologic agent confined to certain areas, as occurs with some other human mycoses.