A 55-year-old man with a 10-year history of bronchiectasis and chronic suppurative lung disease develops nephrotic-range proteinuria and renal insufficiency. Renal biopsy shows amorphous eosinophilic material expanding the mesangium and vessel walls. Congo red stain shows apple green birefringence under polarized light. Immunohistochemistry would most likely demonstrate deposition of:

• A Kappa or lambda light chains
• B Transthyretin
• C Serum amyloid A protein ✓
• D Beta 2 microglobulin

Explanation

Reactive systemic (AA) amyloidosis follows chronic inflammatory states such as bronchiectasis, tuberculosis, osteomyelitis, and familial Mediterranean fever. Hepatically derived serum amyloid A, an acute phase reactant, is deposited as 8 to 10 nm nonbranching fibrils. AL amyloidosis (option A) is associated with plasma cell dyscrasias and shows light chain deposition, while beta 2 microglobulin amyloid occurs in long-term dialysis and transthyretin amyloid affects nerves and heart in familial forms.

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.