Author: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, May 2014.
Pityriasiform seborrhoeide is an unusual variant of seborrhoeic dermatitis. Seborrhoeic dermatitis is a common flaky skin form of dermatitis that mainly affects scalp and skin folds around the ears and face. Pityriasiform seborrhoeide is more widespread and inflammatory than usual seborrhoeic dermatitis.
Pityriasiform seborrhoeide is characterised by:
Pityriasiform seborrhoeide is thought to be a hypersensitivity dermatitis related to the presence of common Malassezia yeasts on the skin surface.
It is not infectious, and generally does not recur once it has been effectively treated.
Diagnosis is usually made by the clinical appearance and by the exclusion of other similar skin conditions such as psoriasis (circumscribed red scaly plaques), pityriasis rosea (herald patch, fir-tree distribution, not affecting scalp or ears) or pityriasis versicolor (less flaky, tends to involve central trunk).
Skin swabs for bacterial culture may be taken if there are oozing areas, as these are often related to Staphylococcus aureus. Skin scrapings for mycology may show yeast forms, but may also be negative, as the hypersensitivity reaction can eliminate them.
Pityriasiform seborrhoeide can be treated topically using a combination of:
Emollients are in general unhelpful and may even aggravate the rash.
If pityriasiform seborrhoeide is extensive or not responding to topical therapy, oral treatment may be necessary.
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