Multiple myeloma

Definition

• Monoclonal proliferation of plasma cell line causing disease

Classification

Monoclonal gammopathy of unknown significance (MGUS)

• M-protein present but <30 g/L, and
• Plasma cells <10% of bone marrow
• Absence of multiple myeloma end-organ damage
• If IgM, must also have no symptoms of a proliferative disorder or hyperviscosity
  • Must think about Waldenstrom macroglobulinemia

Smoldering myeloma

• IgG or IgA M-protein >30 g/L or urinary M-protein (Bence-Jones) >500 mg/24h or plasma cells 10-60%
• Absence of multiple myeloma end-organ damage

Multiple myeloma

• SLiM CRAB symptoms
  • Sixty percent plasma cells in marrow
  • Light chain ratio (κ:λ or λ:κ) >100
  • MRI showing at least two focal lesions
  • Hypercalcemia >2.75 mmol/L
  • Renal failure with creatinine >177 µmol/L or CrCl <40 mL/min
  • Anemia with hemoglobin <100 g/L
  • Bony lytic lesions

Diagnosis

• Routine bloodwork
  • CBC with peripheral blood film, for anemia
  • Calcium and creatinine
  • SPEP with immunofixation
  • Quantitative immunoglobulins
  • Urinalysis
  • UPEP with immunofixation
• Bone marrow biopsy
• Imaging
  • Bone survey including spine, pelvis, skull, humeri, and femurs
  • Add low-dose whole-body CT or MRI for smoldering myeloma and solitary plasmacytoma

Complications

• Acute kidney injury
  • Light chain deposition
  • Hypercalcemia
  • Urate crystals
  • Amyloid deposition
  • Myeloma infiltration