Multiple myeloma

#msk #haematology

part of Plasma cell proliferative disorders

Clinical

most common manifesting symptoms are:
- Fatigue (often from normocytic normochromic anemia due to marrow infiltration)
- Bone pain (due to intraosseous proliferation of abnormal plasma cells and possible fracture)
major cause of death = infection and renal failure

Laboratory

Most patients with multiple myeloma have abnormal serum proteins
Rouleaux formation on peripheral blood smear
Bence-Jones proteins are found in approximately 50% of cases
Elevated ESR common due to high protein burden
3% of patients will not have abnormal proteins in both their serum or urine, a condition termed "nonsecretory myeloma"

Diagnostic criteria

Either of

bone marrow analysis shows ≥10% clonal bone marrow plasma cells
biopsy-proven bone/soft tissue Plasmacytoma
plus
myeloma defining event
- end-organ damage (CRAB)
  - C: hypercalcemia
  - R: renal insufficiency
  - A: anemia
  - B: bone lesions (seen on PF, CT, PET/CT)
- malignancy biomarker (i.e., you can diagnose active myeloma even without CRAB)
  - clonal cell concentration >60%
  - FLC ratio ≥100 or ≤0.01 + clonal plasma cells ≥10%
  - At least one focal lesion ≥5 mm on MRI, involving bone or bone marrow.

Imaging

osteolytic lesions are readily seen in radiographic skeletal survey in 80% of cases.
however, radiographic skeletal survey is insensitive to early marrow disease, hence MRI or PET/CT is preferred for early detection.
extra-medullary disease is present in 1-2% at the time of presentation
- 8% throughout the disease course

See also: Serum Biomarkers in Plasma Cell Proliferative Disorders