IgA Nephropathy: Does Histologic Grading Really Matter?

IgA nephropathy exhibits considerable histologic variability, ranging from normal histology to diffuse proliferative and crescentic glomerulonephritis (GN), although the majority of cases are characterized by focal or diffuse, predominantly mesangial proliferative GN. A number of different histologic classifications have been devised for IgA nephropathy, focusing on glomerular changes, tubulo-interstitial changes, or both, that demonstrate a significant correlation between histologic grade or score and clinical outcome, most often renal survival. However, the value of histologic grading in guiding the nephrologist’s therapeutic approach to patients with IgA nephropathy remains uncertain, and a recent study demonstrated that mean arterial pressure and severity of proteinuria over time were superior to histologic grading using either of the two most widely used classification systems in predicting the rate of deterioration of renal function in a large cohort of patients with IgA nephropathy. This review will focus on the strengths and weaknesses of currently used histologic grading systems for IgA nephropathy, and how our approach to histologic grading might be changed to make such grading more relevant to nephrologists treating patients with this disease. (Acta Nephrologica 2008; 22: 83-88)