Seborrhoeic dermatitis is a chronic/relapsing dermatitis that affects the sebaceous glands of the scalp, face, and trunk. It presents as erythematous plaques with greasy, yellowish scales. Malassezia yeast colonisation plays a role in the development of seborrhoeic dermatitis, alongside genetic and environmental factors. The yeast also causes pityriasis versicolor.
- Risk factors
- Yeas infection with the lipophilic yeasts Malassezia globosa and Malassezia restricta
- Immunosuppression
- Genetic predisposition
- Hormonal factors – androgens may influence the development of seborrhoeic dermatitis
- Psychological stress
- Parkinson’s disease
- Pathophysiology
- Increased sebum excretion rate → proliferation of lipophilic yeasts → yeasts metabolize sebum into free fatty acids, which cause inflammation
- Inflammatory response to Malassezia → hypersensitivity reaction leading to inflammation
- Disruption of the skin barrier due to increased transepidermal water loss → dryness and flaking of the skin
- Hyperproliferation and abnormal differentiation of keratinocytes → scaling
- Signs and symptoms
- Eczematous lesion on a sebum-rich area
- Differentials
- Treatent
- Ketoconazole 2% shampoo for scalp disease
- Selenium sulphide
- Clotrimazole or miconazole for seborrhoeic dermatitis of the face and body
- Topical corticosteroids for severe itching
