Natural History of Idiopathic IgA Nephropathy and Factors Predictive of Disease Outcome

Among the numerous studies published in the last 20 years that have calculated the actuarial renal survival and tried to individuate the prognostic role of the clinical and histologic features present at the onset of the disease or the time of biopsy, we chose to critically analyze the results of the most valid (23 studies). Actuarial renal survival at 10 years in adults was between 80% and 85% in most of the European, Asian, and Australian studies, but was lower than this in studies from the United States and exceeded 90% in the few studies on children. Concordance existed in this selected literature on the fact that impairment of renal function, severe proteinuria, and arterial hypertension are the strongest and more reliable clinical predictors of an unfavorable outcome. Extent of proteinuria during follow up was an even stronger predictor. In adult patients, a high score of the glomerular and tubulointerstitial lesions predicted a more rapid progression. When the single lesions were analyzed separately, glomerular sclerosis and interstitial fibrosis appeared to be the strongest, most reliable predictors of unfavorable prognosis. More controversial was the role of crescents and capsular adhesions.