Yeasts play an important role in the development of seborrhoeic dermatitis but the exact mechanism is not known. Control of the yeasts improves symptoms.
Aetiology
- Although the causes of seborrhoeic eczema are not fully understood, the yeast Malassezia ovale (M. ovale), formerly known as Pityrosporum ovale, is known to play a role
- It is unclear as to how M. ovale induces inflammation and scaling, although there is a hypothesis that the yeast hydrolyzes sebum to release a mixture of saturated and unsaturated fatty acids. The fatty acids are taken up by the yeast but the unsaturated fatty acids remain and breach the skin's barrier function causing the inflammatory reaction
- Seborrhoeic eczema is more common and can be much more severe in patients with HIV and in Parkinson's disease
Referral Criteria:
- Referral should only be considered if patient is responding inadequately to treatment
Formulary, Chapter 13. Skin: Treatment of seborrhoeic dermatitis
Assessment
History
- It is most commonly seen in patients aged 18 to 40 but can occur at any age
- It is more common in males
- Itch is not a predominant feature
- Symptoms fluctuate and the condition may last for years
Clinical findings
Distribution, it affects areas rich in sebaceous glands:
- Scalp and behind the ears. More extensive involvement of the ears with otitis externa may occur
- Face - medial eyebrows (can be associated with chronic blepharitis), glabella and nasolabial folds. Areas under spectacles or hearing aids may also be involved
- Upper trunk - presternal and interscapular regions
- Flexures - axillae, groins, umbilicus, anogenital and submammary regions
Morphology:
- Red, sharply marginated macules / patches covered with greasy-looking yellowish scales
Differential Diagnoses
Referral
Referral should only be considered if patient is responding inadequately to treatment.
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