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Malassezia infections

Malassezia yeasts are a type of fungus. The genus Malassezia is now thought to be composed of several different species. There is some controversy as to whether specific species cause different skin diseases. Species names include:

• M. dermatis
• M. equi
• M. furfur
• M. globosa
• M. obtusa
• M. pachydermatis
• M. restricta
• M. slooffiae
• M. sympodialis
• M. ovalis (also known as Pityrosporum ovale)

Skin conditions caused or aggravated by infection by malassezia include:

• Pityriasis versicolor – most often due to the subspecies M. globosa
• Malassezia folliculitis
• Seborrhoeic dermatitis, dandruff and sebopsoriasis
• Neonatal cephalic pustulosis, a pustular eruption on young babies that resembles infantile acne
• Gougerot-Carteau disease (confluent and reticulated papillomatosis), a pigmented eruption occurring mainly on the chest, back and neck of adolescent girls
• Invasive pityrosporosis
• Some facial atopic dermatitis

Malassezia infections

Malassezia folliculitis

Pityriasis versicolor

Seborrhoeic dermatitis

Diagnosis

The diagnosis of malassezia infections is made from skin scrapings. Microscopy using potassium hydroxide (KOH) preparations shows clusters of yeast cells and long hyphae. The appearance is said to be like "spaghetti and meatballs".

Malassezia species are difficult to grow in the laboratory so scrapings may be reported as "culture negative". The yeast grows best if olive oil is added to the culture medium.

Predisposing factors to infection

Malassezia species inhabit the skin of many adults without causing harm. Unfortunately in some people the yeast proliferates resulting in a skin disorder. The cause is not usually known. However, predisposing factors include:

• Humidity
• Sweating
• Oily skin

Treatment

Consult DermNet's pages on the individual skin conditions to learn about treatment.

In general, malassezia infections are treated with topical or oral antifungal agents. Seborrhoeic dermatitis may also treated with topical steroids.