A retrospective analysis of the natural history of primary IgA nephropathy worldwide.

The worldwide medical literature was reviewed to determine whether the prevalence, clinical presentation, and immunohistologic findings of primary IgA nephropathy were related to geographic areas. A total of 68 reports containing detailed clinical histories and laboratory findings were analyzed. The selected articles were grouped according to their geographic origin: Asia, Australia, Europe, and North America (Canada and the United States). Analysis of the data showed that IgA nephropathy is more frequent in the Asian area than in Australia, Europe, and North America. The male/female ratio indicates that males are more likely to be affected by the disease, particularly in the second and third decade of life. The appearance of the disease is characterized by microscopic hematuria and mild proteinuria in Asians, whereas gross hematuria is more frequent in American and European patients. At the time of renal biopsy, fixed microscopic hematuria is detected in a high percentage of patients in Asia and Europe, whereas macroscopic hematuria is more frequent in American patients. Mild renal lesions occur more frequently in Asian patients, while severe renal lesions and a high frequency of immunoglobulin and complement deposits are present in American and European patients. Differences encountered in this retrospective analysis may be influenced by two important factors: (1) the absence of urinalysis screening programs in the schools of Europe and North America, and (2) the different approaches to renal biopsy in the eastern and western parts of the world. Due to the high rate of renal insufficiency and end-stage kidney disease in European and North American patients with IgA nephropathy, it is recommended that a program of urinalysis screening in schools and an appropriate renal biopsy policy be adopted in the western areas of the world.