Tehran University of Medical Sciences Iranian Journal of Parasitology 1735-7020 18 2 2023 06 27 237 243 Abdulsamet Erden Ankara City Hospital, Clinic of Rheumatology, Ankara, Turkey Berkan Armağan Ankara City Hospital, Clinic of Rheumatology, Ankara, Turkey Serdar Güven Ankara City Hospital, Clinic of Rheumatology, Ankara, Turkey Özlem Karakaş Ankara City Hospital, Clinic of Rheumatology, Ankara, Turkey Fatma Erden Department of Dermatology, Ankara Yıldırım Beyazıt University, Ankara, Turkey Bahar Özdemir Ankara City Hospital, Clinic of Rheumatology, Ankara, Turkey Ahmet Omma Ankara City Hospital, Clinic of Rheumatology, Ankara, Turkey Orhan Küçükşahin Division of Rheumatology, Department of Internal Medicine, Ankara City Hospital, Yıldırım Beyazıt Universi-ty, Ankara, Turkey 2021 10 30 2023 01 22 Background: We aimed to investigate the frequency of Demodex infestation and clinical implications in connective tissue disease patients with facial erythema. Methods: Patients diagnosed with a connective tissue disease and had facial erythema were consecutively enrolled in the study from 2019-2020. An age and gender matched control group was formed from healthy volunteers. Presence of Demodex was investigated by standardized skin surface biopsy. Number of Demodex mites over 5 per centimeter square was considered meaningful for infestation. Topical or systemic metronidazole treatment was given to the connective tissue disease patients with Demodex infestation. Facial erythema visual analog scale was questioned in patients at treatment onset and one month after. Results: A total of 31 connective tissue disease patients with facial erythema were enrolled. Control group included 31 healthy volunteers. Demographics and comorbidities were similar between groups. Demodex infestation was present in 58.1% of the disease group and in 25.8% of the control group (P=0.01). Pruritus was the most common symptom in patients with infestation. Median (IQR) facial erythema visual analog scale score was 6 (3) at treatment onset and was 2 (2.5) one month later (P<0.001). Conclusion: When evaluating facial cutaneous lesions, Demodex infestation should not be overlooked in a patient group like connective tissue diseases with dysfunctional immune system. https://ijpa.tums.ac.ir/index.php/ijpa/article/view/3494 https://ijpa.tums.ac.ir/index.php/ijpa/article/download/3494/1292