A 58-year-old man on long-term hemodialysis develops progressive carpal tunnel syndrome, shoulder pain, and radiographically evident subchondral bone cysts and erosions. Biopsy of the wrist tissue shows amorphous eosinophilic deposits staining with Congo red. The precursor protein of these amyloid deposits is:

• A Islet amyloid polypeptide
• B Transthyretin
• C Beta-2 microglobulin ✓
• D Immunoglobulin lambda light chain

Explanation

Dialysis-associated amyloidosis is caused by deposition of beta-2 microglobulin, a normal component of MHC class I molecules that is cleared exclusively by glomerular filtration. In renal failure it accumulates and forms amyloid preferentially in osteoarticular structures, producing carpal tunnel syndrome, shoulder pain, and lytic bone lesions. Transthyretin causes senile cardiac and familial amyloid polyneuropathy, amylin affects pancreatic islets in type 2 diabetes, and light chains cause AL amyloidosis.

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.