IgA glomerulonephritis: light microscopic and immunohistological studies.

Renal biopsy material of 50 patients suffering from IgA glomerulonephritis was studied by light microscopy, immunofluorescence and occasionally electron microscopy. Associated with a uniform immunohistological pattern mainly focal or diffuse mesangial proliferative glomerulonephritis was found. In addition to the glomerular changes the importance of frequent extraglomerular, mainly vascular and interstitial, alterations is stressed. In arterioles and arteries, deposition of a hyalinous substance was observed. Immunohistology revealed the presence of immunoglobulins and/or C3 in the vessels. In the interstitium fibrinogen/fibrin was often seen, accompanied by chronic inflammatory infiltration and fibrosis.