Unusual phenotypes of diabetic nephropathy: A case report

The prevalence and incidence of diabetes mellitus (DM) are rapidly increasing worldwide. Diabetic kidney disease (DKD) is a chronic complication of DM and major cause of end-stage renal disease. The pathogenesis of DKD is complex, with various clinical features, pathological phenotypes, and poor therapeutic outcomes. DKD rarely occurs in patients without a history or evidence of DM. We herein report a case of diabetic nephropathy (DN) diagnosed using a renal biopsy in a patient with impaired glucose tolerance (IGT). Initially, DKD was considered to start with proteinuria preceding renal dysfunction, although in recent decades, many patients with DM without proteinuria develop renal insufficiency. Here, we also present a case of DN with normoalbuminuric renal insufficiency.

We report a case of a 73-year-old man with no history of DM who presented with proteinuria, and a renal biopsy revealed mesangial proliferative glomerulopathy with mild acute tubular injury. Glucose metabolism was examined, and a 75 g oral glucose tolerance test showed IGT. Fundus examination revealed diabetic retinopathy. We also report a case of a 57-year-old man with DM with normoalbuminuric renal insufficiency, whose renal biopsy revealed renal tubulointerstitial damage but only mild glomerular injury.

This study represents two cases of DKD with unusual presentations and highlights the role of renal tubular injury in the development of DKD. In patients without a history of clinically overt DM or proteinuria, DKD may still be considered. Thus, these cases may help clinicians to better understand DKD.