The frequency of incidental mesangial IgA deposition and its clinicopathological features were investigated in patients with minimal change nephrotic syndrome (MCNS) . Mesangial IgA deposition was present in 15/63 patients (23.8 %), and co-deposition of IgA and C3 was present in 10/63 patients (15.9 %). The serum IgA concentration was significantly higher in IgA (+) patients than in IgA (-) patients (341±79 mg/dl vs. 252±99 mg/dl, p=0.034) . The urinary red blood cell count tended to be higher in IgA (+) patients than in IgA (-) patients (12.8±24.9 vs. 5.0±7.9 counts/HPF, p=0.58) . Histologically, no significant differences were observed between IgA (+) and IgA (-) patients. After steroid treatment, 14 patients with mesangial IgA deposition showed complete remission and one patient had persistent proteinuria . The microhematuria also disappeared after steroid treatment in 13/15 patients (86 .7 %), although it reappeared in 6/13 patients (46 %) during reduction of steroid administration. The present study indicated that the incidental mesangial IgA deposition was frequently observed in MCNS patients (23 .8 %) . The phenomenon of mesangial IgA deposition was related to the higher concentration of serum IgA . However, no influence of mesangial IgA doposition in MCNS patients was found on the post treatment amount of proteinuria, renal function and clinical outcome of MCNS.
