Erythematotelangiectatic rosacea may be associated with a subclinical stage of demodicosis: a case-control study

Background Facial densities of Demodex mites have been observed to be greater in patients with demodicosis and papulopustular rosacea than in healthy control patients. In patients with erythematotelangiectatic rosacea (ETR), this density has been observed to be similar to or greater than that of healthy controls. Erythema and telangiectasia, characteristics of ETR, are often observed among patients with pityriasis folliculorum, a discreet demodicosis, suggesting a possible link between these conditions. Objectives To compare the facial Demodex densities of patients with clinical ETR and patients with healthy skin, demodicosis, rosacea with papulopustules, and other facial dermatoses. Methods In this retrospective study, we recorded Demodex densities measured using two consecutive standardized skin surface biopsies (SSSB1 and SSSB2) in 23 patients with ETR, 20 healthy control patients, 590 patients with demodicosis, 254 with rosacea with papulopustules and 180 with other facial dermatoses. Results Patients with ETR had higher Demodex densities (D cm(-2)) than did the healthy controls (mean +/- SEM; SSSB1: 15 center dot 7 +/- 6 center dot 3 vs. 1 center dot 8 +/- 1 center dot 1 D cm(-2), P = 0 center dot 042; SSSB2: 38 center dot 0 +/- 13 center dot 7 vs. 5 center dot 1 +/- 2 center dot 1 D cm(-2), P = 0 center dot 026) and patients with other dermatoses (SSSB1: 0 center dot 4 +/- 0 center dot 1 D cm(-2), P = 0 center dot 004; SSSB2: 1 center dot 3 +/- 0 center dot 3 D cm(-2), P = 0 center dot 004), but lower densities than patients with demodicosis (SSSB1: 82 center dot 7 +/- 4 center dot 2 D cm(-2), P = 0 center dot 008; SSSB2: 172 center dot 2 +/- 7 center dot 7 D cm(-2), P = 0 center dot 001) or rosacea with papulopustules (SSSB1: 86 center dot 6 +/- 7 center dot 3 D cm(-2), P = 0 center dot 027; SSSB2: 197 center dot 0 +/- 12 center dot 1 D cm(-2), P = 0 center dot 002). Conclusions ETR may be associated with nonvisible Demodex proliferation, possibly corresponding to a subclinical stage of demodicosis. Dermatologists should be aware of this potential association and look for subclinical demodicosis in patients with ETR, so that topical acaricidal treatment can be offered if Demodex density is high.