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

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.