Malassezia and associated skin conditions

Overgrowth of the normally harmless yeast Malassezia can lead to various skin condition including seborrhoeic dermatitis, Malassezia folliculitis (Vlachos et al, 2020) and pityriasis versicolor. In extremely rare cases, Malassezia can cause fungaemia in severely immuncompromised patients (Rhimi et al, 2020) or neonates with a CVC receiving TPN (Chen et al, 2020). For more information see DermnetNZ , StatPearls, or a review by Saunte et al (2020).

Identification can be challenging. Malassezia requires lipids (e.g. olive oil) to be added to culture media in order to grow, and certain method adaptations are recommended during antifungal susceptibility testing (Peano et al, 2017). A chromogenic agar is now available from CHROMagar.

Videos

Clinical Mycology: Direct Examination Series: Candida Malassezia [Hot Topic]

Fungus Malassezia on SDA, saline and LPCB mount showing yeast cells and hyphae

“Fungal Skin Infection of Many Colors” (Tinea Versicolor) | Pathogenesis, Symptoms and Treatment

Seborrheic Dermatitis, Psoriasis and Impetigo in Children – Pediatrics | Lecturio

Factsheets

Seborrhoeic dermatitis

NAME(S)
Seborrhoeic dermatitis; dandruff; cradle cap (in babies)

DISEASE
Characterised by excess scaling of the edge of the scalp, face and anterior chest associated with an inflammatory component. The relative contribution of a cell-mediated response (or hypersensitivity) to yeast colonisation of the skin versus ‘simple’ infection of the keratin layer of the skin is poorly understood. Dandruff (or its equivalent in babies, cradle cap) is characterised by excessive scaling but minimal inflammation, and is largely a cosmetic problem.

FUNGI
Malassezia spp. (Pityrosporum spp.). Of these M. furfur, M. globosa and M. sympodialis are pathogenic, M. pachydermatis is acquired from animals (especially dogs) and other species are rare or only found on normal skin.

PREVALENCE
Rare in children after infancy, affects 3-5% of the world’s population or 200-350 million adults

RISK FACTORS
Incidence is 18-80% in HIV-infected patients, and tends to worsen as the immune deficit progresses. More common in Parkinson’s disease and after a stroke.

DIAGNOSIS
Clinical diagnosis, without laboratory confirmation

TREATMENT
Topical imidazole treatments, often with a low potency topical steroid in a combination ointment. Dandruff is usually treated with ketoconazole containing shampoo. Rarely oral azole therapy is required.

OUTCOMES
Cradle cap remits as the baby grows. Seborrhoeic dermatitis and dandruff tend to relapse, and often require ongoing treatment

Involvement of the external ear canal is common in seborrheic dermatitis [From Bechara Y. Ghorayeb]

Cradle cap is relatively common in babies [From DermNetNZ]

Pityriasis versicolor

NAME(S)
Pityriasis versicolor (tinea versicolor)

DISEASE
Superficial skin infection of the upper trunk, usually without an inflammatory component or scaling. Depigmentation, like rain drops, or excess pigmentation over the chest or upper back is typical, especially after sun exposure

FUNGI
Malassezia furfur (Pityrosporum ovale) and other related species

PREVALENCE
Common, especially in tropical and subtropical regions where up to 50% of the adult population may be affected. More obvious and perhaps more common in the summer months in temperate climates. Most common between ages of 20 and 40

RISK FACTORS
Possibly genetic predisposition as family members not living together are more frequently affected

DIAGNOSIS
Microscopy showing budding yeasts cells from the affected area

TREATMENT
There are several topical treatments available containing sulfide selenium, propylene glycol and azole antifungals. Extensive cases sometimes require oral azole treatment with ketoconazole or itraconazole

OUTCOMES
Rates of recurrence are very high. In some cases prophylactic itraconazole (200mg one day per month x 6 months) has been used with a response of 88% at the end of the study