Malassezia yeasts and pityriasis versicolor

Abstract

To analyze the relationships among different Malassezia species and pityriasis versicolor, the only human disease in which the etiologic role of these fungi is fully accepted (although the species implicated remains a matter of discussion). Since 1996, after the taxonomic revision of the genus, a limited number of papers analyzing the role of the different Malassezia species in pityriasis versicolor have been published or were the subject of presentations in congresses; there were only four in the past year. This paper discusses the results of these works, comparing them with results of the authors' most recent study in this field, conducted over the past 16 months. Most of the studies published thus far now show that Malassezia globosa is the predominant species found in the lesions of pityriasis versicolor, at least in temperate climates. The authors' recent findings confirm these results. The etiologic role of M. globosa in pityriasis versicolor is based, even more than on its isolation in a high percentage of cultures, on its identification by direct microscopy as typical globose yeast cells producing pseudohyphae in almost 100% of cases. The confirmation of the pathogenic role of this species in pityriasis versicolor could help in understanding these conditions, which are still unclear, which promote its transformation from the saprophytic stage present in healthy skin to the parasitic one, and could also help in selecting the best therapeutic measures.