Postinfectious glomerulonephritis. Subtypes, clinico-pathological correlations, and follow-up studies

APGN (WHO: diffuse endocapillary proliferative glomerulonephritis) has long been considered one of the best described kidney afflictions, clinically characterized by the sudden development of a nephritic syndrome after a latency period following a nasopharyngeal infection or pyoderma. Proliferation of mesangial and endothelial cells in the endocapillary space, aggregation of polymorphonuclear granulocytes in the capillary lumina, and deposition of predominantly subepithelial immune complexes on the glomerular basement membrane (so-called "humps") are to the present day considered characteristic of renal morphology. However, the nature of the antigen (or antigens) as well as the determining mechanisms in the pathogenesis of APGN still are unclear. Considerable disagreement also exists regarding the prognosis. An analysis of APGN is once again presented to elucidate whether the morphological picture of APGN is really as uniform as has been generally assumed. A large number of kidney biopsies was examined and subjected to the triad of light microscopy (LM), immunofluorescence microscopy (IFM) and electron microscopy (EM). The findings, which were recorded at an early stage of APGN in all cases (i.e. during the first 9 weeks), were related to clinical data, age (childhood or adulthood), and etiology (e.g. streptococci, staphylococci). In addition, clinical and morphological follow-up over a period of up to 10 years in those cases, which had been carefully documented in the early stages, afforded an insight into the dynamics and the prognosis of APGN. Light microscopy of APGN showed a certain spectrum of variation even during the rather limited period of 9 weeks, due to the varying number of granulocytes and a varying degree of cell proliferation, as we could show semiquantitatively. With the triad of methods, especially by IFM and EM, three separate morphological patterns were distinguishable: the starry sky pattern, the garland pattern and the mesangial pattern. Based on clinico-pathological correlations, these patterns were shown to permit the nosological subdivision of APGN. The following features merit special emphasis: The starry sky pattern occurred most often during the first few weeks, the mesangial pattern increased in frequency after the 3rd week, and the garland pattern could occur at any time. In the starry sky and garland patterns immunoglobulins (mainly IgG) generally appeared in combination with C 3. The mesangial pattern was characterized by C 3 appearing alone. These three immunohistological patterns, which also showed transitional and combined forms, had certain characteristic features by electron microscopy.(ABSTRACT TRUNCATED AT 400 WORDS)