Diabetic nephropathy with interstitial nephritis presenting with a false-positive anti-GBM antibody

A 56-year-old male with DM and HTN presented with flank pain and nausea. Review of systems was negative, physical examination was notable for mild hypovolemia and laboratory revealed BUN 51 mg/dl, creatinine (Cr) 5.1 mg/dl (baseline 1.5), Westergren ESR 122 mm/h, fractional excretion of sodium 0.2% and UA positive for blood and protein. Despite volume resuscitation the Cr continued to rise. Urine sediment analysis revealed granular casts, renal tubular epithelial cells and a negative Hansel's stain. Hemodialysis was initiated with Cr 13.7 mg/ dl for dyspnea and dysgeusia. Subsequent laboratory data revealed 2 separate positive anti-GBM antibody titers and prednisone therapy was initiated. Renal biopsy was performed for further diagnostic, therapeutic and prognostic information and demonstrated interstitial nephritis with linear IgG and albumin deposition consistent with diabetic nephropathy. Follow-up antibody titers were negative. prednisone was discontinued and Cr stabilized with conservative therapy. Anti-GBM antibody disease is characterized by circulating IgG antibodies directed against the glomerular basement membrane, specifically the alpha-3 (IV) collagen chain. Anti-GBM nephritis is a rapidly progressive, isolated glomerulonephritis in association with circulating anti-GBM antibodies. A positive immunofluorescence (IF) test is considered diagnostic in the appropriate clinical setting. Therapies include immunosuppressive agents to suppress new antibody production and plasmapheresis to eliminate circulating antibodies. Anti-GBM antibody is not rapidly cleared by steroid therapy and the recovery of renal function is rare if initiation Cr is greater than 7 mg/dl. This case demonstrates that the current ELISA for alpha-3 (IV) collagen is not pathognomonic for anti-GBM nephritis and that renal biopsy with IF for IgG and albumin may be indicated to prevent administration of potentially toxic treatment.