Malassezia(Pityrosporum) Infections of the Skin

Faergemann, Jan

Abstract

The lipophilic yeast Pityrosporum ovale (Malassezia sp.) is a member of the normal human cutaneous flora in adults but also associated with several skin diseases. Treatment of P. ovale related diseases include topical and systemic antifungal therapy In pityriasis versicolor, under the influence of predisposing factors, P. ovale changes from the round blastospore form to the mycelial form. Pityriasis versicolor may be treated with topical treatment. However, with more extensive lesions, in patients with recurrence of the disease or patients not responding to topical therapy short term treatment with oral antifungal drugs is very effective. Recurrence is a great problem in pityriasis versicolor with a recurrence rate of 60% within 1 year. To avoid this oral ketoconazole 400mg once monthly or 200mg on 3 consecutive days every months have a documented effect. Pityrosporum folliculitis is a chronic disease characterized by pruritic follicular papules and pustules located primarily on the upper trunk, neck and upper arms. In direct microscopy clusters of round budding yeast cells are found. The same treatments used for pityriasis versicolor are effective in the treatment of Pityrosporum folliculitis. However, the treatment period has to be prolonged. With topical therapy 3 to 4 weeks of daily treatment and then prophylactic therapy once or twice weekly is often necessary to first clear the disease and then to avoid recurrence. However, due to the presence of P. ovale deep down in the follicle several patients will not be completely cleared with topical therapy and systemic therapy may be necessary. There are now many studies indicating that J9 ovale plays an important role in seborrheic dermatitis. Many of these are treatment studies showing a good effect of antimycotics parallelled by a reduction in number of organisms. Severe seborrheic dermatitis often difficult to treat is associated with AIDS. In peripheral blood from a high number of patients with seborrheic dermatitis we found an increase in number of natural killer T-cells and decreased PHA and Con-A stimulation. Secondary we found low serum IgG antibody titres in patients compared to controls. Other studies have found a reduced lymphocyte stimulation reaction when lymphocytes from patients with seborrheic dermatitis were stimulated with a P. ovale extract. Additionally, IL-2 and IFN gamma pruduction by lymphocytes from patients was markedly depressed and IL-10 sythesis were increased after stimulation with p. ovale extract. Several studies have clearly documented that antifungal therapy is very effective in the treatment of seborrheic dermatitis.