Primary IgA Glomerulonephritis and Schonlein-Henoch Purpura Nephritis: Clinicopathological and Immunohistological Characteristics

A comparative analysis on clinicopathological and immunohistologicalcharacteristics was performed of 205 cases with primary IgAnephritis and 35 with Schönlein-Henoch purpura nephritis(purpura nephritis). Diagnostic criteria for primary IgA nephritiswere set out so that IgA was either the most prominent immunoglobulinor, at least, equal to IgG and/or IgM, if present, irrespectiveof mesangial or peripheral localization. In primary IgA nephritis,one half of the cases were discovered by asymptomatic proteinuria,and one-third presented recurrent upper respiratory tract infectionand gross hematuria, one-fourth abdominal pain and a few casesjoint pain, while purpura nephritis was associated with a significantlyhigher incidence of such systemic symptoms as abdominal andjoint pains, in addition to purpura. Both diseases shared atendency toward conspicuous hematuria in contrast to the modestproteinuria, with normal renal function in three-fourths totwo-thirds. Moreover, four of 35 with purpura nephritis showedpreceding proteinuria and had been regarded as primary IgA nephritisuntil purpura appeared. The glomerular pathology had a commonfeature in that there was frequent occurrence of mesangial proliferativeand focal and segmental lesions. The immunohistology in thetwo diseases was indistinguishable with regard to the glomerularimmunoglobulins and mediators, whether purpura was present orabsent. Thus, we propose a unifying concept that, by analogywith SLE, primary IgA nephritis may be regarded as ‘sinelupo,’ lying on one side of the nosological spectrum withless systemic symptoms, whereas purpura nephritis may occupythe other side with more systemic aspects. Furthermore, we confirmedthe epimembranous granular deposition of IgA in both diseasesas the most characteristic morphological expression of circulatingimmune complexes.