In multiple myeloma, the characteristic 'M-spike' on serum protein electrophoresis represents a homogeneous immunoglobulin produced by the clonal plasma cells. The most common immunoglobulin type associated with this M-spike is:

• A IgA
• B IgM
• C IgD
• D IgG ✓

Explanation

IgG is the most common paraprotein in multiple myeloma (~55% of cases), followed by IgA (~25%). IgM paraprotein is characteristic of Waldenström macroglobulinemia (lymphoplasmacytic lymphoma), not multiple myeloma. IgD myeloma is rare (<1%). Bence-Jones proteinuria (free light chains) may be present alone or accompanying any heavy chain class.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.