The role of kidney biopsy in the diagnosis of membranous nephropathy.

The discovery of the target antigen M-type phospholipase A2 receptor (PLA2R) with the possibility to detect anti-PLA2R antibodies in serum as well as the identification of several other antigens, overall accounting for almost all cases of membranous nephropathy, paved the way to a revolutionary change in the classification of membranous nephropathy. Serum anti-PLA2R autoantibody titers have been found to be highly specific diagnostic and prognostic biomarkers. Therefore, a positive test for anti-PLA2R serology in patients who present with nephrotic syndrome, normal kidney function, and no evidence of another process to account for proteinuria is believed to suffice to make a diagnosis of primary membranous nephropathy, thus removing the need for a renal biopsy. While technological advances will likely allow this proposal to prevail in the near future, the reasons why renal biopsy could still remain a critical tool for the management of membranous nephropathy in real life are discussed.