Multiple myeloma
Description
- Clonal post-germinal-centre plasma cell malignancy in the marrow + monoclonal immunoglobulin
- **Always preceded by MGUS** - a preceding paraprotein is demonstrable in essentially every case
The spectrum
| Clonal marrow PC | M-protein | End-organ | |
|---|---|---|---|
| MGUS | <10% | <30 g/L | None |
| Smouldering | >=10% | >=30 g/L | None |
| Myeloma | >=10% (or plasmacytoma) | Any | CRAB or SLiM |
- Related entities: solitary plasmacytoma (bone or extramedullary), plasma cell leukaemia (circulating clonal PC >=5% / 0.5 x10^9/L), AL amyloidosis, POEMS, MGRS
Paraprotein isotype
- IgG ~60%, IgA ~20-25% (worse prognosis), light-chain only ~15% (no spike on SPEP - needs free light chains)
- IgD, IgE, non-secretory rare
- *IgM paraprotein = Waldenström or lymphoma, not myeloma*
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