Anti-brush border antibody disease is a rare autoimmune disease. Auto-antibodies are targeted against LRP2/Megalin, which is present on the apical brush border of the proximal tubule epithelial cells and is an endocytic receptor for many substances. This disease is typically seen in elderly patients who present with acute kidney injury. On renal biopsy, light microscopy shows acute tubular injury. Granular tubular basement membrane, as well as apical brush border staining for IgG, is seen on immunofluorescence. IgG and LRP2 colocalize along the tubular basement membrane. In this case report, a 55-year-old male with a recent diagnosis of Lupus underwent kidney biopsy for acute kidney injury and proteinuria. He was found to have focal lupus nephritis, class III, as well as anti-brush border antibody disease. Serology for LRP2 antibodies was positive. This is the first case report of this disease in a patient with lupus and is unusual in that the patient is non-elderly. This may be an under-recognized disease, especially in patients with other autoimmune diseases.
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