Epidemiology of IgA Nephropathy: A Global Perspective.

IgA nephropathy (IgAN), or Berger's disease, is the most common primary glomerular disease worldwide, but varies largely in its geographic distribution. A systematic review of 1,619 publications from the five continental regions of the world was performed to assess the prevalence of IgAN in different worldwide regions and analyze factors responsible for geographic differences. All observational studies that described the prevalence and incidence data on glomerulonephritis were considered. IgAN is more frequent in Asian populations (45 cases per million population/y in Japan) than in Caucasians (31 cases per million population/y in France). These differences are owing to some relevant aspects: (1) systematic mass screening of urine in populations, as occurring in some Asian countries (Hong Kong, Japan, Korea, and Singapore), is not common in Western countries; (2) general practitioners and health care professionals in Western countries underestimate persistent microscopic hematuria and/or mild proteinuria in apparently healthy individuals causing late referral to a nephrologist; and (3) nephrologists adopt different indications for kidney biopsy in individuals with persistent urinary abnormalities. In addition, differences also are owing to the source of data, because the frequency of IgAN observed in a nephrology center with a high incidence of kidney biopsies is higher than in a regional renal biopsy registry that receives data from many centers. In conclusion, greater efforts should be made to diagnose IgAN earlier in individuals who manifest persistent microhematuria and/or mild proteinuria and to introduce less stringent indications for kidney biopsies. This preventive approach, followed by early therapy, may reduce the global burden of end-stage kidney disease caused by IgAN.