[Polymorphism of immunoglobulin heavy chain switch region in IgA nephropathy].

We examined the relation between IgA hyperproduction and polymorphism of the immunoglobulin heavy chain switch (S) region in patients with IgA nephropathy. The frequency of the heterozygous phenotype of IgA2 switch region was significantly increased in these patients. The patients showed a significant increase in the amount of serum IgA, IgA bearing cells and levels of proteinuria. We also compared two reports on the S region in Europe, which showed different results, and found different frequencies in the phenotype of the S region. These findings suggest that IgAN patients in various countries show heterogeneity in the S region and that this polymorphism might be associated with IgA hyperproduction and the development of proteinuria in Japanese patients.