A 50-year-old woman with a 20-year history of type 2 diabetes mellitus on hemodialysis for 8 years develops bilateral carpal tunnel syndrome and destructive arthropathy. Congo red staining of synovial tissue shows amyloid with apple-green birefringence. The amyloid precursor protein is beta-2 microglobulin. Which HLA class is beta-2 microglobulin a component of?
- A HLA class II only
- B HLA class I only ✓
- C Both HLA class I and class II
- D Neither HLA class I nor class II
Correct answer: B. HLA class I only
Explanation
Beta-2 microglobulin is the light chain component of HLA class I molecules (HLA-B, A, C). It is non-covalently associated with the heavy chain of MHC class I but is not part of MHC class II (which consists of alpha and beta chains). This is why elevated beta-2 microglobulin in renal failure deposits as dialysis-associated amyloidosis in joints and tendon sheaths.
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.