Prognostic indicators of progressive renal disease in IgA nephropathy: Emergence of a new histologic grading system

IgA NEPHROPATHY is the most common form of primary glomerulonephritis worldwide.’ It was initially considered a benign disease, but subsequent reports of large series of patients showed that approximately 20% to 40% of the patients develop progressive renal disease from 5 to 25 years after diagnosis.2 A substantial number of these patients developed end-stage renal disease (ESRD) requiring dialytic therapy, but the incidence of IgA nephropathy causing ESRD varies geographically. In Australia, 10% to 22% of patients initiated on dialytic therapy have IgA nephropathy.’ Li3 reported that in China, 18.3% of patients with ESRD have IgA nephropathy, which is the leading cause of ESRD in a country that has over 1 billion inhabitants. The incidence of IgA nephropathy as a cause of ESRD in the United States is unknown, but Julian et al’ felt that this disease is substantially underestimated and understudied. Globally, IgA nephropathy therefore stands out as an important health care problem afflicting tens of thousands of patients, with many of them facing the dire consequence of developing ESRD. At the present time, no effective treatment is available. Hence, it is imperative to identify reliable prognostic indicators of progressive renal disease so that therapeutic intervention strategies can be targeted toward the subgroup of patients who are at high risk of developing ESRD. In this review, I will discuss the rationale and scientific basis for the development of a histologic grading system that will help in the prediction of progressive renal disease. The clinical utility and its limitations will also be discussed. IgA nephropathy is a primary glomerular disease; thus, it is speculated that morphologic evi