Disease name and synonyms

Seborrheic dermatitis (dandruff, cradle cap in babies)

Fungi responsible (links to these)

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.

Disease description

Seborrhoeic dermatitis is 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 colonization 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 characterized by excessive scaling but minimal inflammation, and is largely a cosmetic problem.

Frequency and global burden

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

Underlying problems and at risk patients

Incidence of 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.

Diagnostic testing

Clinical diagnosis, without laboratory confirmation.

Treatments

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.

Outlook and prognosis

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