TITLE:
Complement System in Psoriatic Arthritis (PsA): Investigating C3 as a Marker of Disease Activity and Treatment Response
AUTHORS:
Zahra Zaki Al Zahir, Sara Ibrahim Al Hamal, Ahmed Abdulaziz Al Traouti, Ali Al Shali
KEYWORDS:
Psoriatic Arthritis, Disease Activity, Complement C3
JOURNAL NAME:
Open Journal of Rheumatology and Autoimmune Diseases,
Vol.15 No.4,
November
18,
2025
ABSTRACT: Introduction: Psoriatic arthritis (PsA) is a chronic inflammatory arthritis commonly associated with psoriasis, affecting 10% to 30% psoriasis patients. Complement component C3 has been suggested as a potential biomarker for disease activity in PsA, with elevated levels reported in moderate to severe disease that may normalize after treatment. Objectives: To investigate the relationship between complement C3 and disease activity in PsA. Methods: A prospective observational study was conducted at the Rheumatology Outpatient Clinic of Qatif Central Hospital, Saudi Arabia, involving 55 patients with active PsA. Complement activation was assessed using C3, ESR, and CRP levels before and after biological therapy. Results: There were no significant differences in median ESR and CRP levels before and after treatment based on gender (p > 0.05). Males had significantly higher baseline C3 levels compared to females (p = 0.025), but post-treatment C3 levels showed no significant difference (p = 0.332). Based on DAPSA, 46 patients (83.6%) had low disease activity, while 9 patients (16.4%) had moderate disease activity. No significant changes in C3 were observed following treatment. Conclusions and Recommendations: Patients with mild to moderate PsA exhibit normal C3 levels at baseline and after biological therapy, indicating that C3 behaves as a mild acute phase reactant rather than a sensitive biomarker of disease activity. Further studies are needed to assess the utility of complement components in PsA, particularly more severe disease.