Although the glomerular lesions in this case were mild according to the diabetic nephropathy criteria based on mesangial matrix expansion, TMA-like lesions in the glomeruli and severe interstitial lesions, which were not included in the diabetic nephropathy criteria, were clearly involved in the renal damage in this case, suggesting that DPP4 inhibitors were involved in renal damage via a mechanism different from that of the conventional mechanism. This evidence concerns the gene DPP4 and diabetic kidney disease.