Fungal infections in patients with psoriasis or atopic dermatitis

Both, psoriasis and atopic dermatitis are multifactorial diseases with an unknown pathogenesis. To elucidate the influence of fungal infections in the onset or recurrence of those inflammatory skin disease we determined the frequencies of Candida and dermatophyte infections of the skin and orointestinal tract concomitantly seen in patients with psoriasis or atopic dermatitis. We analyzed the files of more than 40 000 in-patients of the Department of Dermatology, Kiel. Sex- and age-adjusted relative risks-were calculated. The results demonstrate that patients with psoriasis (N = 3006) presented with a decreased rate of tinea. This was significant for tinea corporis (RR = 0.13, p < 0.01). Candida infections of the skin were seen more often in psoriasis patients compared to controls. Differentiating between Type I (early onset) and Type II (late onset) psoriasis only Type I psoriasis patients presented with decreased dermatophyte infections and increased Candida colonization of the intestinum. However, patients with Type II psoriasis demonstrated an increased rate of candidosis cutis and candidosis oris as compared to controls. Patients with atopic dermatitis (N = 1808) displayed a decreased overall incidence of tinea and Candida infections. Furthermore, in patients with atopic dermatitis a Candida colonization of the orointestinal tract was found elevated (RR = 1.51, p < 0.01), whereas tinea corporis (RR = 0.24, p < 0.01) and candidosis cutis (RR = 0.30, p < 0.001) was found decreased compared to controls. Our results show that the influence of fungal infections on the two skin diseases investigated is not as strong as often considered. The increased relative risk in patients with atopic dermatitis to present with Candida colonization in the digestive tract or vice versa may contribute to the pathogenesis of atopic dermatitis.