Background: Certolizumab pegol is used to treat ankylosingspondylitis, Crohn’s disease, psoriatic arthritis, and rheumatoidarthritis. Unlike other monoclonal antibodies such as infliximaband adalimumab, certolizumab does not contain an Fc fraction andhence does not induce complement activation. In this report, wedescribe the case of a patient with thrombotic microangiopathycaused due to certolizumab pegol, with a brief description about thepathophysiological approach to thrombotic microangiopathy.Case Report: A-39-year-old man suffering from ankylosingspondylitis for the past 10 years presented with fatigue. He had beenon certolizumab pegol treatment for 6 months, starting with 400 and200 mg every 2 weeks. He had significant nonimmune hemolyticanemia and thrombocytopenia without a disseminated intravascularcoagulopathy. Schistocytes were observed in more than 10% of theerythrocytes per field. Plasma exchange along with corticosteroidtreatment was started. There was a dramatic improvement withina week, and after 10 sessions of plasma exchange, the patient wasdischarged on corticosteroids with a tapering plan. ADAMTS13enzyme activity was determined to be normal.Conclusion: The development of drug-induced thromboticmicroangiopathy may be either immune-mediated or dose-dependenttoxicity-mediated Anti-drug antibodies and their immunologicalaspects are still unclear and yet to be elucidated.