canis - Articles
Myeloma
Synonym(s): Multiple myeloma, plasma cell myeloma, plasma cell neoplasm
Introduction
- Accounts for 8% of all hematopoietic tumors.
- Cause: proliferation of neoplastic plasma cells in bone marrow.
- Signs: non-specific, hyperviscosity.
- Diagnosis: laboratory results, bone marrow cytology, radiographic lesions.
- Treatment: chemotherapy (melphalan and prednisolone).
- Prognosis: may be controlled with treatment.
Presenting signs
- Vague signs of illness:
- Anorexia.
- Lethargy.
- Weight loss.
- Pyrexia.
- Polyuria/polydipsia.
- Hyperviscosity syndrome:
- Cerebral dysfunction.
- Ocular changes.
- Congestive heart failure Heart: congestive heart failure.
- Bone pain or lameness.
- Bleeding disorder:
- Epistaxis.
- Gingival bleeding.
- Bruising.
- Petechiation.
Age predisposition
- Mean age of onset 8 years.
Cost considerations
- Extensive investigations required for diagnosis.
- Long-term chemotherapy usually required.
- Regular blood samples required to monitor chemotherapy and therefore ongoing costs.
Special risks
- High serum viscosity occurs in ~20% of dogs with multiple myeloma (MM) and can → bleeding diathesis, bizarre neurologic signs and retinal abnormalities.
- MM involving vertebrae can → vertebral fractures/collapse and spinal cord compression.
- Hypercalcemia Hypercalcemia: overview , hyperviscosity syndrome, and renal disease all increase anesthetic risk.
Pathogenesis
Etiology
- Unknown.
- Possible causes - genetic predisposition, viral infection (but not FeLV or FIV), chronic immune stimulation, exposure to carcinogens.
Pathophysiology
- Proliferation of neoplastic plasma cells usually → secretion of monoclonal immunoglobulin (paraprotein) → hyperviscosity and other clinical signs.
- Neoplastic plasma cells proliferate in bone marrow.
- In most cases these cells secrete an abnormal immunoglobulin (paraprotein) (usually IgA or IgG heavy or light chain fragments) → excretion of immunglobulin leads to renal tubular damage.
- The paraprotein may be a cryoglobulin.
- Hyperproteinemia or monoclonal gammopathy affects platelet function and may interfere with clotting mechanisms.
- Increased serum viscosity (particularly with IgA secreting myelomas) → circulatory impairment with cardiovascular, respiratory, neurological and ocular signs (hyperviscosity syndrome).
- Some non-secretory myelomas have been reported.
- Antibody coating of red blood cells → hemolysis (Coomb's positive anemia).
- Increased percentage of plasma cells in marrow → anemia, leukopenia and thrombocytopenia.
- Abnormal plasma cells → reduced immune function.
- Hypercalcemia seen in 20% of cases.
- Anemia due to reduced marrow synthesis and increased RBC fragility.
Timecourse
- Insidious onset.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- Chaffin K et al (1998) Extramedullary plasmacytoma in the trachea of a dog. JAVMA 212 (10), 1579-1581 PubMed.
- Hendrix D V H et al (1998) Ophthalmic disease as the presenting complaint in five dogs with multiple myeloma. JAAHA 34 (2), 121-128 PubMed.
- Villiers E & Dobson J (1998) Multiple myeloma with associated polyneuropathy in a German Shepherd Dog. JSAP 39 (5), 249-251 PubMed.
- Hammer A S & Couto C G (1994) Complications of multiple myeloma. JAAHA 30 (1), 9-14 VetMedResource.
Other sources of information
- Vail D M (2007)Plasma cell neoplasms.In:Small Animal Clinical Oncology.4th edn. Eds S J Withrow & E G MacEwen. Philadelphia: W B Saunders & Co. pp 769-782.
- Vail D M (2000)Hematopoietic tumors. In:Textbook of Veterinary internal Medicine.5th edn. Eds S J Ettinger & E C Feldman. Philadelphia, PA: W B Saunders Co. pp 516-520.