Glucocorticoid therapy for acute interstitial nephritis in a patient with diabetic nephropathy: A case report

RATIONALE: Acute interstitial nephritis (AIN) can cause acute kidney injury. Diabetic nephropathy (DN) is a chronic microvascular complication of diabetes. The coexistence of these diseases complicates diagnosis and treatment. PATIENT CONCERNS: A 41-year-old man with diabetes and hypertension presented with dizziness on 4 January 2025. His renal function was normal 7 months previously, but his sCr was 258 μmol/L immediately before admission and peaked at 299 μmol/L after admission. The patient reported use of an unidentified herbal decoction during the previous month. DIAGNOSES: A biopsy showed acute tubular injury (70% of tubules), mild tubulitis (<5% of tubules), and interstitial inflammatory infiltration (~10% of cortex), consistent with AIN. The glomerular findings met the 2010 Renal Pathology Society criteria for class IIa DN. There was no infection or systemic autoimmune disease. The herbal decoction was a possible trigger. INTERVENTIONS: Prednisone was started on 15 January 2025 (0.52 mg/kg/d), followed by tapering and discontinuation. Repaglinide and insulin were used for glycemic control. Dapagliflozin was added at follow-up for glycemic normalization and renoprotection. Hypertension was treated, but no adjustments were required after glucocorticoid initiation. OUTCOMES: At discharge, the sCr was 194 μmol/L. At the follow-up (March 19, 2026), there were improvements in the sCr, eGFR, blood urea nitrogen, HbA1c, and 24-h urinary protein, and these clinical parameters were about the same at the last follow-up (April 9, 2026). The antidiabetic regimen was continued unchanged, and the most recent HbA1c was 5.6% (March 19, 2026). The patient developed corticosteroid-associated hyperglycemia and insomnia. The hyperglycemia was successfully managed with insulin, and the insomnia improved during corticosteroid tapering. Dapagliflozin was subsequently added for glycemic control and kidney protection. No infection was recorded. LESSONS: Kidney biopsy should be considered when a patient with diabetes develops acute kidney dysfunction because AIN can coexist with DN. This patient's kidney function improved after initiation of prednisone, but antihypertensive therapy was intensified before prednisone treatment. Glycemic therapy was then modified, and the possible offending herbal decoction was previously discontinued. Although we only examined a single patient with AIN and DN, glucocorticoid therapy may have contributed to the resolution of AIN.