Characteristic Renal Histology of a 81-Year-Old Patient with a 30-Year History of Diabetes Mellitus: A Case Report

New interpretation of diabetic nephropathy or diabetic kidney disease from kidney biopsy: review article

Many nephrologists considered that renal involvement in diabetes patients was seen as nodular glomerulosclerosis (i.e., Kimmelstiel-Wilson lesions). However, they diagnosed diabetic nephropathy or diabetic kidney disease (DKD) from clinical information on diabetes history, and reports of evaluation by kidney biopsy were scarce. Since the publication of the Tervaert classification of diabetic nephropathy in 2010, reports of kidney biopsy in these patients have increased. Analysis of biopsy specimens revealed not only the Tervaert classification (class I to IV) based on glomerular lesions, but also various other pathologies. Besides nodular lesions, findings included paratubular basement membrane insudative lesions (PTBMILs), polar vasculosis, and nephropathy associated with novel drugs (sodium-glucose transport protein 2 inhibitors and dipeptidyl peptidase-4 inhibitors). PTBMILs are unique to diabetic nephropathy. In patients with continuous hyperglycemia and excessive salt intake, elevated blood osmolality (calculated by serum Na × 2 + serum glucose/18 + serum urea nitrogen/2.8) leads to thirst and excessive drinking, which results in fluid overload and generalized edema. The increase in circulating blood volume is thought to induce PTBMILs because of the influx of serum components into the endothelium of glomerular vessels. This case series review presents diverse kidney biopsy findings in patients with diabetic nephropathy or diabetic kidney disease as well as the pathogenesis.

Thrombotic Microangiopathy, Podocytopathy, and Damage to the Renal Tubules with Severe Proteinuria and Acute Renal Dysfunction Induced by Lenvatinib

Lenvatinib, a tyrosine kinase inhibitor (TKI), is a stronger inhibitor of vascular endothelial growth factor receptor, fibroblast growth factor receptors 1 to 4, and platelet-derived growth factor receptor (PDGFR) than other TKIs. We herein report a 77-year-old Japanese woman who received the minimum dose of lenvatinib for treatment of hepatocellular carcinoma. Within one month of starting treatment, she developed severe proteinuria, hypertension, and renal dysfunction. A kidney biopsy showed drug-induced thrombotic microangiopathy, podocytopathy, and polar vasculosis. We also observed damage to the renal tubules, where PDGFR is located. To our knowledge, this is the first report of lenvatinib-induced damage to the renal tubules.

Nodular-like glomerular lesion after long-standing chronic renal infection in a patient with medullary sponge kidney and mild hyperglycemia

A 63-year-old Japanese woman was admitted to our institute for the evaluation of proteinuria. The patient was diagnosed with medullary sponge kidney, distal type renal tubular acidosis, and renal infection at the age of 37. Thereafter, the patient had repeated renal infections. Urinary proteinuria appeared at around the age of 61 and gradually increased up to 1.0 g daily. In the same period, glycated hemoglobin (HbA1c) increased to 7.0%. On kidney biopsy, light microscopy showed a nodular glomerular lesion and capsular drop. Linear staining for immunoglobulin G along the glomerular basement membrane was observed by immunofluorescence. Electron microscopy showed thickening of the glomerular basement membrane to a width of 800–900 nm. A class III glomerular lesion was diagnosed according to the Tervaert classification. This case indicates that mild but prolonged hyperglycemia for more than 10 years may also contribute to the formation of nodular lesions, although long-standing repeated chronic renal infection and chronic acidosis may have been a precipitating factor in the formation of diabetic nephropathy, including nodular glomerular lesions. This hypothesis is of interest because nodular lesions specific to diabetes are currently considered to be associated with long-term severe hyperglycemia.

Learning points

Nodular glomerular lesions in diabetes mellitus are thought to be associated with long-term severe hyperglycemia.

This case shows that although mild, long-term hyperglycemia for more than 10 years may also contribute to the formation of nodular lesions and that repeated chronic kidney infections over the years and chronic acidosis may be facilitating factors in the formation of diabetic nephropathy, including nodular glomerular lesions.

This case appears to be idiopathic nodular glomerulosclerosis of the medullary sponge kidney associated with chronic urinary tract infection.