Telmisartan-induced type 4 renal tubular acidosis: a case report

Hyperkalemia is a common electrolyte disturbance in hospitalized patients, often caused by impaired renal potassium excretion due to hypoaldosteronism. Type 4 Renal Tubular Acidosis (RTA), commonly associated with diabetes mellitus and RAAS-inhibiting medications, is a significant consequence. We report a 56-year-old male with diabetes, hypertension, and coronary artery disease who developed type 4 RTA after starting telmisartan post-hip replacement. His course was complicated by pneumonia and worsening hyperkalemia, with arterial blood gas showing Normal Anion Gap Metabolic Acidosis (NAGMA) and a positive urinary anion gap. Discontinuing telmisartan and initiating hydrocortisone led to significant renal function improvement and potassium normalization. This case highlights the importance of caution when using RAAS inhibitors in high-risk patients and supports hydrocortisone as a viable alternative when fludrocortisone is unavailable.