Which immunoglobulin isotype is most commonly elevated in multiple myeloma?

Question

Accepted Answer

D. IgG. ## Immunoglobulin Isotypes in Multiple Myeloma

**Key Point:** IgG is the most frequent monoclonal immunoglobulin in multiple myeloma, accounting for approximately 50–60% of all cases.

### Distribution of Isotypes in MM

| Isotype | Frequency | Clinical Notes |
| --- | --- | --- |
| IgG | 50–60% | Most common; produces hyperviscosity less frequently than IgM |
| IgA | 20–25% | Second most common; higher risk of renal involvement |
| IgD | 2–3% | Rare; often presents with advanced disease |
| IgM | <1% | Extremely rare in MM; more typical of Waldenström macroglobulinemia |
| Light chain only | 15–20% | Bence Jones proteinuria; high risk of myeloma kidney |

**High-Yield:** The classic triad of MM is: (1) monoclonal protein spike on serum/urine electrophoresis, (2) bone marrow plasma cells >10%, and (3) CRAB criteria (Calcium elevation, Renal insufficiency, Anemia, Bone lesions). IgG is the most frequent culprit in this triad.

**Clinical Pearl:** Although IgG is most common overall, IgA myeloma has a higher propensity for renal damage due to its larger molecular size and propensity to form polymers, leading to cast nephropathy (myeloma kidney).

**Mnemonic:** **GOAD** — IgG is the most common (remember "G" for "Gold standard" of MM), followed by IgA, then Others (IgD, IgM), then light chain-only (D for "Dimerized" or "Dimer-prone").

Answer

A. IgM

Answer

B. IgA

Answer

C. IgE

Which immunoglobulin isotype is most commonly elevated in multiple myeloma?

Explanation

Immunoglobulin Isotypes in Multiple Myeloma

Distribution of Isotypes in MM

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Isotype	Frequency	Clinical Notes
IgG	50–60%	Most common; produces hyperviscosity less frequently than IgM
IgA	20–25%	Second most common; higher risk of renal involvement
IgD	2–3%	Rare; often presents with advanced disease
IgM	<1%	Extremely rare in MM; more typical of Waldenström macroglobulinemia
Light chain only	15–20%	Bence Jones proteinuria; high risk of myeloma kidney