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Pityrosporum yeasts--what's new?
1Department of Dermatology, Sahlgrenska University Hospital, Göteborg, Schweden.
Abstract:
The lipophilic yeast Pityrosporum ovale is a member of the normal human cutaneous flora in adults but also associated with several skin diseases. In pityriasis versicolor, under the influence of predisposing factors, P. ovale changes from the round blastospore form to the mycelial form. A great problem in pityriasis versicolor is the high rate of recurrence and to avoid this a prophylactic treatment is mandatory. 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 disease responds rapidly to antimycotic therapy. There are now many studies indicating that P. ovale plays an important role in seborrhoeic dermatitis. Many of these are treatment studies showing a good effect of antimycotics paralleled by a reduction in number of organisms. Severe seborrhoeic dermatitis often difficult to treat is associated with AIDS. In peripheral blood from a high number of patients with seborrhoeic 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 seborrhoeic dermatitis were stimulated with a P. ovale extract. Additionally, IL-2 and IFN gamma production by lymphocytes from patients was markedly depressed and IL-10 synthesis were increased after stimulation with P. ovale extract. The majority of adult patients with atopic dermatitis localized to the head, neck and scalp are prick-test positive to a protein P. ovale extract. One study showed that p. ovale extracts increased IL-4, IL-10 and IgE synthesis in patients with atopic dermatitis. There are also treatment studies indicating that antifungal treatment may be beneficial in these patients.
Insights
Pityrosporum ovale, a common skin yeast, is linked to various skin conditions like pityriasis versicolor, folliculitis, seborrheic dermatitis, and atopic dermatitis. Antifungal treatments show promise for these P. ovale-associated skin diseases.
Area of Science:
- Dermatology and Mycology
- Human Cutaneous Microbiome Studies
- Immunodermatology
Background:
- Pityrosporum ovale (P. ovale) is a lipophilic yeast part of normal adult skin flora.
- It is implicated in several skin diseases, including pityriasis versicolor, pityrosporum folliculitis, seborrheic dermatitis, and atopic dermatitis.
- The yeast's morphology can shift from blastospore to mycelial forms, particularly in pityriasis versicolor.
Purpose of the Study:
- To review the role of Pityrosporum ovale in common human skin diseases.
- To summarize current understanding of P. ovale's association with pityriasis versicolor, folliculitis, seborrheic dermatitis, and atopic dermatitis.
- To highlight the therapeutic implications of targeting P. ovale in these conditions.
Main Methods:
- Literature review of studies investigating Pityrosporum ovale and associated skin conditions.
- Analysis of clinical observations and treatment outcomes for pityriasis versicolor and pityrosporum folliculitis.
- Summary of immunological findings in seborrheic dermatitis and atopic dermatitis patients related to P. ovale.
Main Results:
- Pityrosporum folliculitis responds well to antifungal therapy.
- Seborrheic dermatitis patients show altered immune responses to P. ovale, including changes in T-cells and cytokine production (decreased IL-2, IFN-gamma; increased IL-10).
- Atopic dermatitis patients often exhibit positive prick tests to P. ovale extracts, with associated increases in IL-4, IL-10, and IgE.
Conclusions:
- Pityrosporum ovale plays a significant role in the pathogenesis of pityriasis versicolor, pityrosporum folliculitis, seborrheic dermatitis, and atopic dermatitis.
- Antifungal treatment is crucial for managing pityrosporum folliculitis and shows potential benefit in seborrheic and atopic dermatitis.
- Understanding the immune interactions with P. ovale is key to developing effective prophylactic and therapeutic strategies for these skin conditions.