Malassezia

Malassezia is a genus of lipophilic yeasts in the family Malasseziaceae, within the Basidiomycota. Members are common components of the normal skin microbiota of humans and many animals, especially in sebaceous areas such as the scalp, face, chest, and back.

Several species are associated with human disease. The best known are Malassezia furfur (formerly Pityrosporum ovale) and Malassezia globosa, with others including M. sympodialis and M. restricta. Some species, such as Malassezia pachydermatis, are more prominent on animals. These yeasts are adapted to grow in lipid-rich environments and often require exogenous long-chain fatty acids for growth, making lipid-enriched culture media useful for laboratory identification.

Clinical relevance arises from colonization and overgrowth in the skin. Malassezia is implicated in tinea versicolor (pityriasis versicolor), characterized by hypo- or hyperpigmented macules on the trunk and proximal limbs. It can also cause Malassezia folliculitis, presenting as pruritic follicular papules or pustules, and is associated with inflammatory skin conditions such as seborrheic dermatitis and dandruff. The pathogenic mechanisms involve lipid degradation products and inflammatory responses that can alter pigmentation and skin sensation.

Diagnosis is supported by microscopy showing yeast cells and short hyphae in skin scrapings, a appearance described as spaghetti and meatballs on potassium hydroxide preparation. Cultures require lipid-rich media. Identification can be achieved through biochemical, MALDI-TOF, or molecular methods; microscopy and clinical context are often decisive in routine practice.

Treatment includes topical antifungals (azole or ciclopirox preparations; selenium sulfide or zinc pyrithione shampoos) and, for extensive or refractory disease, systemic antifungals such as itraconazole or fluconazole. Recurrence is common, reflecting persistent colonization in sebaceous skin.