A 65-year-old man presents with fatigue, bone pain, serum calcium 11.8 mg/dL, creatinine 2.4 mg/dL, and a monoclonal IgG spike on serum protein electrophoresis. Bone marrow biopsy shows 35% plasma cells. The M-protein is most likely produced as a result of:
- A Neoplastic proliferation of a single clone of plasma cells secreting identical immunoglobulin ✓
- B Polyclonal B-cell expansion secondary to chronic infection
- C Heavy chain class switching from IgM to IgG in reactive lymph nodes
- D Increased IL-6 driving polyclonal immunoglobulin synthesis
Correct answer: A. Neoplastic proliferation of a single clone of plasma cells secreting identical immunoglobulin
Explanation
Multiple myeloma arises from a malignant clone of plasma cells that secretes a structurally identical (monoclonal) immunoglobulin, producing the M-protein spike. This is distinct from polyclonal hyperglobulinemia seen in infections. IL-6 is important in myeloma pathogenesis but drives the clonal expansion, not polyclonal synthesis.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.