Demodicosis and rosacea: epidemiology and significance in daily dermatologic practice

Demodicoses are thought to be rare, occurring mainly for patients with immunosuppression.

We sought to demonstrate the high frequency of demodicoses and the overlapping with papulopustular rosacea (PPR) .

We conducted a prospective epidemiologic study among 10 dermatologists. High Demodex density (Dd) was confirmed by standardized skin surface biopsy.

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.

Demodicoses are frequent and occur among patients who are immunocompetent. PPR with normal Dd are rare.