A 48-year-old man with long-standing bronchiectasis and chronic suppurative lung disease develops progressive renal failure and nephrotic-range proteinuria. Renal biopsy shows amorphous eosinophilic material expanding the mesangium and vessel walls. The material stains with Congo red and shows apple-green birefringence under polarized light. Immunostaining is positive for serum amyloid A protein. The underlying renal lesion is:

• A AL (primary) amyloidosis with lambda light chain deposition
• B Light chain deposition disease
• C Fibrillary glomerulonephritis
• D AA (secondary reactive) amyloidosis ✓

Explanation

Chronic suppurative inflammation such as bronchiectasis drives sustained hepatic overproduction of serum amyloid A, which deposits as AA amyloid in glomeruli, vessels, and interstitium. Reactivity for serum amyloid A confirms AA type. AL amyloid (option A) stains for kappa or lambda light chains and occurs with plasma cell dyscrasias. Fibrillary GN (option C) is Congo red negative. Light chain deposition disease (option B) lacks Congo red positivity and shows granular linear staining along basement membranes.

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.