Molecular genetics in IgA nephropathy

Evidence from both genotypic and phenotypic perspectives is considered that patients may be genetically predisposed to IgA nephropathy (IgAN) or Henoch-Schönlein purpura (HSP) or that a factor(s) might exclusively contribute to their progression to chronic renal failure. In contrast to most other renal diseases, both IgAN and HSP are uncommon in blacks; this is unexplained but is not due to their low frequency of the A2m(1) allotype. The association of these diseases or their progression with a variety of abnormalities of IgA immunobiology in patients and their families has not been linked to any genotype; similarly, no HLA antigen has been positively or negatively associated in any consistent way. Although complement factor 3 universally accompanies IgA glomerular deposition, complement pathway abnormalities are only sporadically reported with either IgA deposition or disease progression. Whether angiotensin-related polymorphism including the converting enzyme alleles have a specific predictable role, particularly in the progression of renal failure in IgAN, remains problematic. The promising possibility that a structural defect in IgA1 due to an as yet unidentified genetic defect accounts for the deposition of IgA is considered in some detail. Nevertheless, the genetic mechanism(s) of progressive renal failure, whether exclusive to IgAN or to glomerular diseases generally, is of paramount importance.