Malassezia infections: a medical conundrum.

Malassezia yeasts have long been considered commensal fungi, unable to elicit significant damage. However, they have been associated with a diversity of cutaneous diseases, namely pityriasis versicolor, Malassezia folliculitis, seborrheic dermatitis, atopic dermatitis, psoriasis, and confluent and reticulate papillomatosis. Several hypotheses have been proposed to explain the pathogenic mechanisms of these fungi, but none have been confirmed. More recently, such organisms have been increasingly isolated from bloodstream infections raising serious concern about these fungi. Given the difficulty to culture these yeasts to proceed with speciation and antimicrobial susceptibility tests, such procedures are most often not performed and the cutaneous infections are treated empirically. The recurring nature of superficial skin infections and the potential threat of systemic infections raise the need of faster and more sensitive techniques to achieve isolation, identification, and antimicrobial susceptibility profile. This article reviews and discusses the latest available data concerning Malassezia infections and recent developments about diagnostic methods, virulence mechanisms, and susceptibility testing.