smoldering myeloma
Meaning of smoldering myeloma: Myeloma already present in the marrow and visible in the blood, but not yet doing the organ damage that defines the disease needing treatment.
Definition of smoldering myeloma
Smoldering myeloma is an early stage of plasma cell cancer in which abnormal plasma cells have built up in the bone marrow and are producing a single abnormal protein, while no organ damage has yet appeared. It sits between an incidental protein finding and active multiple myeloma. There are no symptoms, and it is usually picked up on blood or urine testing done for some other reason.
Where does it sit on the scale?
| Stage | Marrow and protein | Organ damage |
|---|---|---|
| Monoclonal gammopathy | Small amounts of both | None |
| Smoldering myeloma | Substantially raised | None |
| Active multiple myeloma | Raised | Present |
The three describe one continuous process cut into sections. The cut points are drawn where they are because they predict how quickly things change, not because anything different is happening biologically at the boundary.
What counts as organ damage?
Four findings do the work, and their presence is what moves a case out of this category. Calcium in the blood rises as the tumor eats into bone. Kidney function falls, usually because light chain fragments of the abnormal protein clog the filtering tubes. The red cell count drops as the marrow fills up with plasma cells. Bone develops punched-out holes, which weaken it and can lead to a fracture through ordinary use. A small group without any of these is nonetheless treated as active disease, because an extreme burden of plasma cells or an extreme imbalance of light chains predicts damage so reliably that waiting for it serves no purpose.
Why does the wording about protein cause confusion?
Because the abnormal protein is described as a monoclonal antibody, which is also the name of a whole class of manufactured drugs. Here it means something different: identical copies of one immunoglobulin churned out by a single clone of plasma cell myeloma cells, useless as a defense and measured only as a marker of how much tumor is present. The manufactured kind is deliberately designed and given as treatment. Reports usually avoid the ambiguity by calling the tumor product a paraprotein or an M protein rather than a monoclonal antibody.
Also known as
Used in a sentence
Smoldering myeloma was diagnosed after a paraprotein was found on routine testing.
Good to know
The abnormal protein here is a monoclonal immunoglobulin produced by the tumor itself, which is a different thing from a monoclonal antibody manufactured as a medicine, although both are described by the same phrase.