Multiple Myeloma

Description

• Normal cells transform into myeloma cells at the hematopoietic stem cell level
• Pathologic derangements:
  • Tumor cells within marrow lead to bone destruction and cytopenia
  • Immunodeficiency develops secondary to suppression of normal immune functions
  • Myeloma proteins lead to hyperviscosity and amyloidosis
  • Multifactorial renal failure
• Plasma cell secretions activate osteoclasts, leading to:
  • Bone lysis, pathologic fractures, and neurologic impairment
  • Hypercalcemia (exacerbated by impaired renal function)
• Anemia due to marrow infiltration and renal insufficiency
• Immunocompromised due to:
  • Decrease in the number of normal immunoglobulins
  • Qualitative and quantitative defects in T- and B-cell subsets
  • Granulocytopenia
  • Decreased cell-mediated immunity
• Hyperviscosity secondary to protein accumulation:
  • Leads to high-output congestive heart failure
• Myeloma light chains accumulate in the renal epithelial cells and destroy the entire nephron
• Clinical signs such as anemia, renal insufficiency, or lytic bone lesions
• Complications:
  • Pathologic fractures
  • Hypercalcemia
  • Renal failure
  • Recurrent infection
  • Anemia
  • Spinal cord compression (10% of all multiple myeloma [MM] patients)

Etiology

• Incidence: 4/100,000 population:
  • 1% of all cancers
  • 10% of all hematopoietic malignancies
  • 10,000 deaths/yr
• Mean age at diagnosis is 66 yr
• Slightly higher incidence in men and African Americans (reason unknown)

• Rarely seen in children
• <2% in patients <40 yr of age