Immune checkpoint inhibitor-associated myocarditis and fulminant type I diabetes in a patient with metastatic non-small cell lung cancer

A woman in her mid-60s presented to the hospital due to a history of nausea, vomiting, shortness of breath, dyspnoea on exertion and polyuria. She was receiving medical therapy for advanced non-small cell lung cancer and recently initiated immune checkpoint inhibitor (ICI) immunotherapy. Investigations revealed lab results consistent with diabetic ketoacidosis (DKA), elevated cardiac biomarkers, multiple cardiac arrhythmias and reduced ejection fraction on transthoracic echocardiogram. Cardiac catheterisation showed non-obstructive coronary arteries. The patient was diagnosed with an ICI-associated myocarditis and type I diabetes due to recent initiation of the ICI durvalumab. She was treated with the institutional DKA protocol and received corticosteroid therapy for drug toxicity according to guidelines. She was discharged with marked improvement in symptoms. The patient had good recovery after discharge with further investigations showing improvement in her cardiac ejection fraction on cardiac MRI. She remains on medical therapy with an insulin regimen for diabetes management.