Pityrosporum ovale and skin diseases.

Pityrosporum ovale is a lipophilic yeast belonging to the normal human cutaneous flora in adults. It is not only a saprophyte but also an opportunistic pathogen associated with: Pityriasis versicolor, Pityrosporum folliculitis, seborrhoeic dermatitis and some forms of atopic dermatitis. Even systemic infections have been described. In pityriasis versicolor P. ovale change from the blastospore to the mycelial form under the influence of predisposing factors such as high temperature, high relative humidity or endogenous factors such as greasy skin, sweating, heredity, immunosuppressive treatment or disorders. Topical treatment is often effective but short term treatment with fluconazole, ketoconazole or itraconazole is also effective. The great problem is 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. Under the influence of the same predisposing factors as in pityriasis versicolor P. ovale increase in numbers in the hair follicles. The main differential diagnosis is acne vulgaris. The effect of antifungal treatment is often dramatic. 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 parallelled by a reduction in number of P. ovale. Severe seborrhoeic dermatitis often difficult to treat is associated with AIDS. In a recent study we have evidence for a slight T-cell defect in many patients with seborrhoeic dermatitis.(ABSTRACT TRUNCATED AT 250 WORDS)