A 45-year-old man with longstanding type 2 diabetes has nephrotic-range proteinuria and renal biopsy shows Kimmelstiel-Wilson nodules. Immunohistochemistry reveals these nodules stain with which combination of markers, confirming their nature?

• A Positive Congo red with apple-green birefringence — confirming amyloid nodular glomerulosclerosis
• B Positive PAS with lambda light chain restriction — confirming light chain deposition disease
• C Positive PAS, negative Congo red, positive collagen IV — confirming matrix accumulation in diabetic nephropathy ✓
• D Positive fibronectin staining — confirming fibronectin glomerulopathy as the etiology

Explanation

Kimmelstiel-Wilson (KW) nodules are acellular mesangial nodules composed of accumulated extracellular matrix (laminin, type IV collagen, fibronectin). They are strongly PAS-positive (reflecting glycoprotein/glycan content), negative for Congo red (ruling out amyloid), and positive for collagen IV immunostaining. KW nodules must be distinguished from amyloidosis (Congo red-positive, apple-green birefringence) and light chain deposition disease (monoclonal light chain immunostaining, similar nodular pattern but with linear GBM deposits).

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.