In multiple myeloma, the characteristic monoclonal immunoglobulin spike on serum protein electrophoresis (SPEP) is called the M-spike. Which immunoglobulin class is most commonly overproduced?
- A IgA
- B IgM
- C IgG ✓
- D IgD
Correct answer: C. IgG
Explanation
IgG is the most commonly overproduced immunoglobulin in multiple myeloma, accounting for approximately 55–65% of cases. IgA follows at about 20–25%, IgD and IgE are rare, and IgM monoclonal protein is more characteristic of Waldenström macroglobulinemia (lymphoplasmacytic lymphoma). Light-chain-only myeloma accounts for 15–20% and produces Bence-Jones proteins without an intact heavy chain.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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