Epidemiology

IgA nephropathy (IgAN) is the commonest pattern of glomerulonephritis worldwide, it accounts for approximately 10% to 50% of biopsy-proven primary glomerular diseases.[10] In one systematic review, the estimated annual global incidence of IgAN in adults was 2.5 in 100,000.[11] Annual incidence in the US has been estimated at 1.29 in 100,000.[12] IgAN affects nearly all ages, but the peak incidence is in the second and third decades of life.[13][14] There is regional variability with incidence of IgAN higher in Asian people than people from Europe, the US, or Africa.[11][13]

These rates may differ, at least in part, due to differences in public health screening and biopsy practices. In countries with active screening programs for kidney disease, and centers with a low threshold to perform a kidney biopsy, the reported incidence of IgAN is higher, as more patients with mild disease are identified. However, autopsy and genetic data also suggest that IgAN may be more common in Asian populations.[15]

A clearly defined west-to-east increase in disease incidence, and distribution of currently understood genetic risk alleles, occurs from North America to Asia. The precise contribution of specific alleles, however, remains unclear.

In the four extensively published familial IgAN kindreds, the genetic linkage differs in each kindred.[16][17][18][19] Genome-wide analysis has identified several genetic susceptibility loci, but these do not map to the loci identified in the published familial IgAN kindreds.[20][21][22][23] 

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