Drug‐Induced Liver Injury During Treatment With Tocilizumab: A Case Report of an Atypical Pattern Lesion

ABSTRACT Tocilizumab is an interleukin‐6 (IL‐6) receptor antagonist indicated for various rheumatologic conditions. While hepatotoxicity is a recognized adverse effect, it predominantly manifests as hepatocellular injury. We report a rare case of drug‐induced liver injury (DILI) presenting with a cholestatic pattern and cholangitis features in a 75‐year‐old patient treated for giant cell arteritis. Following the third tocilizumab infusion, the patient developed jaundice and abdominal pain. Laboratory investigations revealed a cholestatic pattern of liver injury (ALT/ALP ( R ) ratio ≤ 2) with marked cholestasis. Imaging findings raised suspicion for cholangitis. After ruling out infectious, autoimmune, and metabolic aetiologies, a liver biopsy confirmed neutrophilic cholangitis and marked intrahepatic and sinusoidal cholestasis. Drug discontinuation, along with ursodeoxycholic acid treatment, led to clinical and biochemical resolution. This case is notable as tocilizumab‐induced liver injury rarely presents with cholangitic features. The pathophysiology may involve the disruption of IL‐6 signaling, which plays a pivotal role in maintaining biliary epithelial integrity. Clinicians should be vigilant for this atypical cholestatic presentation to ensure prompt drug withdrawal.