[MCNS, which secondary developed into incidental IgA nephropathy--a case report].

There have been a number of case reports on nephrotic syndrome with histological findings of minimal change on light microscopy and mesangial IgA deposition on fluorescent microscopy. The pathogenesis of these cases is, however, yet to be clarified. Here, we report a case of minimal change nephrotic syndrome (MCNS) associated with IgA nephropathy, which developed later in the course of MCNS. The patient was 18 years old male with steroid-responsive nephrotic syndrome. First episode of proteinuria occurred when he was 4 years old. On the fourth episode of proteinuria, renal biopsy revealed minimal change on light microscopy and no evidence of deposition of immunoglobulins or complements on immunofluorescent and electron microscopy. On the fifth relapse of MCNS, microhematuria developed concomitantly with massive proteinuria. Renal biopsy, then, showed light microscopic findings of mild focal segmental glomurulonephritis. Significant mesangial IgA deposition was observed on immunofluorescence study. Electron microscopy revealed electron dense deposit in the mesangial and paramesangial area. The patient was well-responsive to steroid although microhematuria persisted after disappearance of proteinuria. We concluded that IgA nephropathy may have developed subsequently in the course of MCNS in our case.