Supplementary Material for: Immune Checkpoint Inhibitor - Associated Renal Tubular Acidosis and Nephrogenic Diabetes Insipidus - A Case Report

Introduction: Immunotherapy has significantly changed the landscape of cancer treatment, yet it can lead to immune-related adverse events (irAEs), including renal complications. This report highlights a unique case of tubular injury associated with Pembrolizumab in a patient with malignant melanoma. Case Presentation: A 42-year-old female patient with malignant melanoma received adjuvant Pembrolizumab treatment. Three months later, she presented with profound weakness, myalgia, abdominal pain, polyuria, and thirst. Laboratory tests revealed acute kidney injury (AKI), significant proteinuria, renal tubular acidosis (RTA) with severe electrolyte imbalances, and nephrogenic diabetes insipidus (NDI). Management involved withholding Pembrolizumab, initiating high-dose prednisone therapy, and correcting hypokalemia and metabolic acidosis. The patient showed rapid clinical improvement, with normalization of renal function and symptom resolution, allowing for discharge within a week. A follow-up visit confirmed no residual renal impairment. Conclusion: This case emphasizes the importance of recognizing renal complications in patients undergoing treatment with immune checkpoint inhibitors (ICIs). Awareness of potential adverse effects such as RTA and NDI is crucial for prompt identification and management to prevent lasting damage.