A case report of immune checkpoint inhibitor‐related myositis and cholangitis induced by pembrolizumab.

Key Clinical Message: Rare but severe, immune‐related adverse events such as myositis and sclerosing cholangitis can occur with immune checkpoint inhibitors in lung cancer treatment. This case report highlights their co‐occurrence after pembrolizumab treatment, indicating the need for vigilance and management strategies in immune checkpoint inhibitors therapy. Immune checkpoint inhibitors (ICI) are used in advanced treatment of lung cancer but can lead to immune‐related adverse events. ICI‐related myositis and cholangitis are rare, and their combination has not been previously reported. Here, we report the first case of ICI‐related myositis and sclerosing cholangitis. A patient with stage IV lung adenocarcinoma who received one cycle of pembrolizumab with cisplatin and pemetrexed developed myositis. Treatment with prednisolone improved the myositis, but the patient subsequently developed cholangitis. The patient did not respond to a regimen of prednisolone, mycophenolate mofetil, and azathioprine, and eventually died due to worsening lung cancer. An autopsy confirmed the presence of ICI‐related myositis and sclerosing cholangitis. [ABSTRACT FROM AUTHOR]