Dermoscopic Response Predictors in Papulopustular Rosacea Treated with Topical Ivermectin and Metronidazole: A Prospective Observational Comparative Study

Background: Over recent years, dermoscopy has proven useful not only for diagnosing skin conditions but also as a tool for predicting treatment response in inflammatory dermatoses. However, no data are available on dermoscopic predictors in papulopustular rosacea (PPR). Objective: To evaluate whether certain clinical and dermoscopic findings serve as positive or negative predictors of response to topical ivermectin or metronidazole in PPR. Methods: Twenty-three patients with moderate-to-severe PPR were enrolled. Ten patients received ivermectin 10 mg/g cream and 13 received metronidazole 1% gel (non-randomized, based on physician preference), applied once daily for 8 weeks. Inflammatory lesion counts and key clinical/dermoscopic features were assessed at baseline and after 8 weeks by two independent, blinded physicians. Post-treatment clinical outcomes (optimal response: >75% lesion reduction; partial response: 50–75% reduction) were correlated with baseline features. Results: Both treatments significantly reduced inflammatory lesion counts (p<0.001 for both). Any response (optimal or partial) occurred in 7/10 (70%) ivermectin-treated and 8/13 (62%) metronidazole-treated patients. Optimal response occurred in 5/10 (50%) ivermectin-treated and 4/13 (31%) metronidazole-treated patients. In the ivermectin group, all patients who achieved optimal response had baseline protruding follicular plugs (PFPs) (5/5, 100%) in dermoscopy, which are indicators of demodex tails. Those with partial or minimal/no response in the ivermectin group did not have baseline PFPs (0/5). Baseline PFPs were significantly associated with optimal response to ivermectin (p=0.004). In the metronidazole group, all 4 optimal responders did not have baseline PFPs. All the 4 patients in the metronidazole group with baseline PFPs showed minimal/no response, though this was not statistically significant (p=0.176). No other baseline features significantly predicted response in either treatment group. Conclusion: PFPs in dermoscopy of moderate-to-severe PPR serve as positive predictors for optimal response to topical ivermectin, but not metronidazole. This observation warrants validation in larger controlled trials.