Clinicopathological characteristics of the focal and segmental form of idiopathic membranous nephropathy: comparison with the typical form of this disease.

Although idiopathic membranous nephropathy (IMN) is thought to represent a diffuse glomerulopathy, it was found that three of 31 children histologically diagnosed as IMN showed focal and segmental deposition of immunoglobulin G (IgG) and C3 on the glomerular capillary walls. The present study attempted to comparatively investigate clinical and pathological features of the diffuse group and the focal segmental group in 31 IMN children. Immunofluorescence study revealed that 28 of 31 IMN exhibited diffuse granular deposition of IgG along glomerular capillary walls. In contrast, focal and segmental deposition of IgG and C3 was noted in three children with IMN. In addition, focal and segmental electron-dense deposits were identified in these cases. In two children of the focal segmental group, immunofluorescent patterns of IgG deposition were unchanged even at the second biopsy. The focal segmental form of IMN tended to occur in younger children than diffuse IMN. However, other clinical parameters such as the range of proteinuria, hematuria, serum albumin and prognosis did not show any significant differences between both groups. Electrophoretic profiles of urinary proteins on sodium dodecylsulfate-polyacrylamide gel electrophoresis were not different between both groups. It is proposed that the focal segmental form of IMN may have a distinctive glomerulopathy from the typical form of IMN.