A 62-year-old man has nephrotic-range proteinuria with mild renal impairment. Serum free light chain assay shows elevated kappa light chains. Renal biopsy light microscopy shows nodular glomerulosclerosis resembling diabetic nephropathy. Immunofluorescence shows linear granular staining along glomerular and tubular basement membranes restricted to a single light chain isotype. Congo red stain is negative. The most likely diagnosis is:

• A Fibrillary glomerulonephritis
• B AA amyloidosis
• C Diabetic nodular glomerulosclerosis
• D Light chain deposition disease ✓

Explanation

Light chain deposition disease, usually kappa restricted, produces nodular glomerulosclerosis that closely mimics diabetic nephropathy, with monotypic linear granular basement membrane staining on immunofluorescence. The decisive finding distinguishing it from amyloid is the negative Congo red stain, because LCDD deposits are nonfibrillar granular electron-dense deposits rather than beta pleated fibrils. Diabetic nodules would be Congo red negative but would lack monotypic light chain restriction on immunofluorescence.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.