A 52-year-old man on maintenance hemodialysis for 15 years develops bilateral carpal tunnel syndrome and shoulder pain. Synovial biopsy shows amorphous deposits staining with Congo red and showing apple-green birefringence. The precursor protein forming these amyloid fibrils is:
- A Serum amyloid A
- B Immunoglobulin light chain
- C Beta 2 microglobulin ✓
- D Transthyretin
Correct answer: C. Beta 2 microglobulin
Explanation
Dialysis-associated (hemodialysis related) amyloidosis is caused by deposition of beta 2 microglobulin, the light chain of MHC class I molecules. Normally cleared by glomerular filtration, it accumulates in patients with end-stage renal disease and forms periarticular, osteoarticular, and synovial deposits causing carpal tunnel syndrome, shoulder pain, and bone cysts. Serum amyloid A defines secondary amyloidosis, light chains define AL amyloidosis, and wild-type transthyretin causes senile systemic cardiac 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.