A 48-year-old man maintained on long-term hemodialysis for 14 years develops progressive bilateral carpal tunnel syndrome, flexor tendon nodules, and lytic bone cysts of the wrist. Biopsy of the wrist tissue shows amorphous eosinophilic deposits staining with Congo red. The precursor protein of these deposits is:

• A Calcitonin
• B Transthyretin
• C Beta-2 microglobulin ✓
• D Amylin (islet amyloid polypeptide)

Explanation

Dialysis-associated (Abeta2m) amyloidosis arises because beta-2 microglobulin, normally cleared by glomerular filtration, accumulates in patients with end-stage renal failure on long-term dialysis. It deposits preferentially in osteoarticular structures, producing carpal tunnel syndrome, shoulder pain, flexor tenosynovitis, and subchondral bone cysts. Transthyretin causes familial and senile cardiac amyloid, calcitonin-derived amyloid is seen in medullary thyroid carcinoma, and amylin deposits in pancreatic islets in type 2 diabetes.

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.