Malassezia

Chapter 228 Malassezia

Members of the genus Malassezia include the causative agents of tinea versicolor and have been associated with other dermatologic conditions and with fungemia in patients with indwelling catheters. Malassezia are commensal lipophilic yeasts with a predilection for the sebum-rich areas of the skin. They are considered a part of the normal skin flora, with presence established by 3-6 mo of age.

The history of Malessezia nomenclature is complex and can be confusing. Because the yeast forms may be oval or round, these organisms were formally designated Pityrosporum ovale and Pityrosporum orbiculare. Newer technologies have allowed an improved classification system, with 13 recognized species. Only Malassezia pachydermatitis, a zoophilic yeast that causes dermatitis in dogs, is not lipophilic.

Transformation of the yeast form to a hyphal form facilitates invasive disease. The clusters of thick-walled blastospores together with the hyphae produce the characteristic spaghetti and meatballs appearance of Malassezia.

Malassezia globosa, M. sympodialis, M. restricta, and M. furfur are the major causes of tinea versicolor (Chapter 658). Malassezia organisms have also been associated increasingly with other dermatologic conditions. M. sympodialis and M. globosa have been implicated in neonatal acne, and M. globosa and M. restricta

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