Brittle Diabetes Following Partial Pancreatectomy: A Case of Type 3c Diabetes Mellitus Complicated by Type 4 Renal Tubular Acidosis.

Type 3c diabetes mellitus (T3cDM), or pancreatogenic diabetes, is an under-recognized subtype of diabetes resulting from exocrine pancreatic disease or surgery. It is frequently misclassified as type 1 or type 2 diabetes, leading to inappropriate management. Brittle diabetes, characterized by severe glycemic variability and insulin sensitivity, is rare in T3cDM. Type 4 renal tubular acidosis (RTA), or hyperkalemic distal RTA, is another underdiagnosed complication of diabetic kidney disease. We report a unique case of transition to T3cDM presenting as brittle diabetes in a patient with a history of partial pancreatectomy, complicated by type 4 RTA.  This case highlights the clinical challenge of managing brittle diabetes in the context of T3cDM, a condition that often goes unrecognized in patients with a history of pancreatic surgery. The concurrent diagnosis of type 4 RTA complicated glucose and electrolyte management, as insulin is both therapeutic for hyperkalemia and a risk for hypoglycemia in brittle diabetes. Awareness of this overlap is essential, as both conditions require individualized therapy that departs from traditional inpatient diabetes management. Clinicians should maintain a high index of suspicion for T3cDM in patients with pancreatic pathology and unstable glycemic profiles. Accurate diagnosis is key to appropriate treatment and prevention of complications. Additionally, type 4 RTA should be considered in diabetics with unexplained hyperkalemia despite preserved renal function. A multidisciplinary approach is essential for managing the complex interplay between glucose and potassium regulation in such patients.