A Rare Clinical Entity: Anti-tubular Basement Membrane Disease

Introduction: Acute kidney injury (AKI) is well reported after developing auto antibodies against glomerular basement membrane however very little is published about anti-tubular basement membrane disease (Anti-TBM), an entirely different and rare disease entity, as a cause of AKI. Case Description: 83-year-old male with a history of Sjogren's syndrome and monoclonal B-cell lymphocytosis was admitted with AKI with a previously normal serum Creatinine(0.9 mg/dl). Urine analysis was significant for microscopic hematuria. His serological workup was positive for ANA, SSA/SSB, MPO with indeterminate ANCA and negative for anti-GBM,IgG4 and Cryoglobulins. He had normal C3, C4 and miniscule population of B-cells on flow cytometry. Rapidly declining kidney function prompted a kidney biopsy and initiation of renal replacement therapy (RRT). His biopsy yielded a diagnosis of anti-TBM, culminating in the initiation of high dose steroids. No anti-TBM antibody levels were sent due to unavailability at our institution. Plasma exchange was also commenced but discontinued due to inconclusive evidence of lung involvement. His renal function recovered without further RRT after two weeks of prednisone 60 mg, followed by a taper to 40 mg along with initiation of Cyclophosphamide 100mg daily. Discussion: The overall histologic findings of tubulointerstitial nephritis with strong linear proximal tubular basement membrane deposition of IgG and C3 with sparing of glomeruli was diagnostic of anti-TBM disease. Anti-TBM can be of primary or secondary origin. Secondary cases have been reported in association with membranous nephropathy, transplant rejection and urinary infections. Current literature is devoid of any guidelines to monitor disease activity with any markers or treat with any specific immunosuppressive agents. However, anecdotal evidence suggests that plasma exchange, steroids, steroid sparing Immunosuppressive agents and rituximab may have role in the management of anti -TBM. We recommend sending anti -TBM titers, if possible, to monitor the response and to tailor the therapy based on literature review.