Atezolizumab and Bevacizumab Induced Diabetes Mellitus and Myocarditis: A Case Report.

Checkpoint inhibitors such as atezolizumab and bevacizumab have improved outcomes in hepatocellular carcinoma (HCC), but their use can lead to severe immune-related adverse events (IRAEs). We report the case of a 71-year-old man with HCC and multiple comorbidities who developed diabetic ketoacidosis (DKA) secondary to new-onset type 1 diabetes mellitus and myocarditis, five days after his second cycle of atezolizumab and bevacizumab. Laboratory findings demonstrated metabolic acidosis, hyperglycemia, ketonemia, elevated troponin, B-type natriuretic peptide (BNP), C-reactive protein (CRP), deranged liver function, and acute kidney injury. ECG revealed a new right bundle branch block, and echocardiography confirmed impaired left ventricular function. He was managed with standard DKA guidelines, transitioned to a basal-bolus insulin regimen, and commenced on high-dose corticosteroids for myocarditis, with multidisciplinary input from oncology and cardiology teams. This case highlights the importance of early recognition and coordinated management of IRAEs, as well as the need for long-term surveillance for endocrine and cardiac complications following checkpoint inhibitor therapy.