Background: Maturity-onset diabetes of the young (MODY) is an uncommon genetic form of diabetes that arises from mutations in the HNF1B gene. Because it begins at a young age and typically requires insulin therapy, MODY is frequently mistaken for type 1 diabetes. 

Case Presentation: We describe a 13-year-old Marwari boy with a history of type 1 diabetes, recurrent diabetic ketoacidosis DKA, and recurrent urosepsis post-pyeloplasty. Despite high-dose insulin therapy (>240 units/day), glycemic control was inadequate. Genetic analysis confirmed HNF1B-associated MODY (MODY 5).

Conclusion: In young individuals presenting with both diabetes and kidney abnormalities, MODY 5 should be considered as a possible diagnosis. Early recognition and precise diagnosis are crucial for guiding appropriate therapy and genetic counselling.