Comparison of the Prevalences of Demodex folliculorum in Rosacea and Seborrhoeic Dermatitis with Standardized Skin Surface Biopsy

Objective: Rosacea (RSC) and seborrhoeic dermatitis (SD) are inflammatory dermatological conditions which are located in sebaceous gland-rich areas. Demodex folliculorum (D folliculorum) is the most common ectoparasite in humans that may play a role in the aetiopathogenesis of both diseases. The aims of this study were to compare the prevalences of D folliculorum positivity in patients with RSC and SD; compare the positivity in both diseases according to different age ranges and gender and compare mite positivity according to clinical types of RSC. Methods: A total of 200 facial skin biopsies, one from each patient clinically diagnosed as RSC (100 patients) and as SD (100 patients) were studied between February 2011 and August 2013. D folliculorum density was investigated using standardized skin surface biopsy and the specimens were examined under light microscope. Quantitative data were tested with Pearson’s Chi-squared test and Fisher’s exact test, and significance was defined as a p-value of < 0.05. Results: Demodex mite was positive in 51 (25.50%) of the 200 patients (74.51% of them had RSC, and 25.49% had SD; p = 0.0001). No statistical differences were detected between the prevalences of Demodex positivity in patients with RSC in terms of gender (p = 0.768) and age (p = 0.193. In the SD group, there was no statistical difference in mite positivity in terms of gender (p = 0.138), while the positivity was significantly higher in the age group 45 years and over (p = 0.039). In different clinical types of RSC, there was no significant difference with respect to mite positivity (p = 0.168). Conclusion: Positivity of D folliculorum was significantly higher in RSC when compared to SD. Our results suggest that D folliculorum mite can play a more important role in the aetiopathogenesis of RSC than SD.