Demodicosis and rosacea: Epidemiology and significance in daily dermatologic practice

Background: Demodicoses are thought to be rare, occurring mainly for patients with immunosuppression. Objective. We sought to demonstrate the high frequency of demodicoses and the overlapping with papulopustular rosacea (PPR). Methods: We conducted a prospective epidemiologic study among 10 dermatologists. High Demodex density (Dd) was confirmed by standardized skin surface biopsy. Results: In all, 4372 diagnoses, in which 115 were demodicoses, were collected among 3213 patients. Demodicosis was the 9th most frequent diagnosis (13th new). Each dermatologist observed an average of 2.4 demodicoses a week (1.2 new). The proportion of demodicoses varied greatly according to the dermatologist. The general status was good in 110 patients; only 3 had known immunodeficiency. The most frequent symptoms were follicular scales (71%) and telangiectasia (63%). The mean Dd was higher in pityriasis folliculorum (m = 61 D/cm(2)) than in PPR (m = 36 D/cm(2); P = .04); 42 patients with PPR had a high Dd, 6 had a low Dd. Conclusion: Demodicoses are frequent and occur among patients who are immunocompetent. PPR with normal Dd are rare.