What is the classic histology pattern seen in diabetic nephropathy?

• A. Mesangial expansion and glomerular basement membrane thickening with nodular glomerulosclerosis (Kimmelstiel-Wilson lesions)
• B. Crescent formation with fibrin
• C. Amyloid deposition in glomeruli
• D. Tubular atrophy and interstitial fibrosis

Answer: (A)

The classic histology of diabetic nephropathy features mesangial expansion and thickening of the glomerular basement membrane, with nodular glomerulosclerosis (Kimmelstiel-Wilson lesions).

Chronic high blood glucose promotes nonenzymatic glycation of proteins, leading to accumulation of advanced glycation end products in the glomerular basement membrane and mesangium. This causes the mesangial matrix to expand and the GBM to thicken, increasing permeability and contributing to albuminuria. When the mesangial expansion forms nodular, PAS-positive nodules within the glomerulus, these are the Kimmelstiel-Wilson lesions indicative of diabetic nephropathy. The efferent arterioles often develop hyaline arteriolosclerosis, which raises glomerular pressures and accelerates injury.

Other patterns describe different diseases: crescents with fibrin point to rapidly progressive GN; amyloid deposition in glomeruli indicates renal amyloidosis; tubular atrophy and interstitial fibrosis reflect chronic tubulointerstitial damage rather than the defining glomerular changes of diabetic nephropathy.