Case Report: Nine days to nephrotic syndrome, two weeks to remission—clinical tempo suggests minimal change disease hidden behind diabetic nephropathy

Diabetic nephropathy (DN) is the leading cause of end-stage kidney disease, yet non-diabetic kidney disease (NDKD) is found in a substantial proportion of diabetic patients undergoing kidney biopsy, alone or superimposed on DN. Minimal change disease (MCD) is a rare but treatable cause of nephrotic syndrome in this setting, and recognising it matters because immunosuppression—appropriate for MCD—is not indicated for DN. We report a 67-year-old man with four-year type 2 diabetes who presented with nine days of lower-extremity oedema and nephrotic syndrome: 24-hour urinary protein 7,289 mg, urine albumin-to-creatinine ratio (UACR) 7,667.9 mg/gCr, serum albumin 27.2 g/L and serum creatinine 90 µmol/L. Eight months earlier serum albumin was 42.3 g/L with negative dipstick protein and creatinine 62 µmol/L. Renal biopsy on the second hospital day showed diabetic changes without Kimmelstiel-Wilson nodules, basement membrane thickening with foot process effacement exceeding 80%, no electron-dense deposits and negative immunofluorescence. Over eight months of optimised DN-directed therapy proteinuria nevertheless rose progressively to a peak UACR of 13,450 mg/gCr with albumin 16.8 g/L and creatinine 164 µmol/L. Methylprednisolone 60 mg daily for one week was then given together with rituximab 1.0 g on days 1 and 15. UACR fell by 88% to 1,627 mg/gCr within 14 days, partial remission being documented at week 2, and at 24 months UACR was 660 mg/gCr with albumin 42 g/L and creatinine 96 µmol/L. The diagnostic clue was the measured discordance between eight months of deterioration under optimised therapy and two weeks of improvement after immunosuppression, which makes a superimposed podocytopathy of the MCD type the most probable reading. When a diabetic patient deteriorates under optimised DN-directed therapy and then improves within days of immunosuppression, early biopsy and review of the specimen are warranted.