Microvascular disease and the progression of IgA nephropathy.

In order to examine the role of microvascular disease in the evolution of IgA nephropathy (IgAN), the interrelationships among vascular sclerosis, glomerular sclerosis, age, and hypertension were determined by morphometric analysis of renal biopsies in 71 patients with IgAN; 63 age- and sex-matched individuals with minimal change nephrotic syndrome (MCNS) served as normal controls. The following parameters in glomeruli and in vessels with an outer diameter of 60 microns or less were analyzed by multiple regression analysis: (1) percentage of glomeruli with segmental and/or global sclerosis; (2) percentage of vessel area in renal cortical tissue measured by the point-counting method; (3) index of hyaline change estimated as the percentage of the number of arteries showing hyaline change; (4) index of vessel wall thickness determined by the ratio of mural thickness to outer diameter of arteries; (5) number of vascular cross sections counted per 6.25 microns2. The results of the multiple regression analysis demonstrate that glomerular and vascular sclerosis are interrelated and that hypertension and vessel area are almost equally important as predictors of glomerular sclerosis. Vessel area proved to be an early marker of vasculopathy, as its values in IgAN, even in the absence of hypertension and/or glomerular sclerosis, exceeded those in age- and sex-matched controls (with MCNS). These data, obtained by the use of quantitative methods, establish a role for vessel disease and hypertension in the progression of IgAN.