Primary IgA nephropathies in children.

With the worldwide use of immunofluorescence microscopy, idiopathic IgA nephropathy (Berger's disease) has been recognized as a distinct form of primary glomerular disease. IgA nephropathy is the most common form of GN in many parts of the world. However, since the criteria for diagnosis are exclusively based on the findings of predominant IgA in the mesangium, the boundaries of this "entity" are not well delineated and it has become clear that several different clinical conditions share this common immunopathology. IgA nephropathy should, therefore be regarded as a syndrome. Schönlein-Henoch purpura (SHP) and Berger's disease represent the primary form of this syndrome. The clinical features of both diseases in children are reviewed. Although the clinical symptoms may appear different there is a close relationship between SHP and IgA nephropathy. They share the same pathology, the same pathogenesis, and they may both recur on a transplanted kidney. Moreover, both diseases can occur in a single family. When pathologic mechanisms are more defined, SHP may prove to be 1 end of a spectrum of diseases associated with microvascular immune deposits in which IgA is the predominant immunoglobulin seen, the other end being Berger's disease.