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Myeloma-Related Disorders in Cats

What are Myeloma-related Disorders?

Myeloma is a type of cancer that affects plasma cells. Plasma cells are specialized lymphocytes, i.e. they are part of the white blood cell group and are key components of the immune system. In the healthy individual, plasma cells are responsible for making antibodies and help protect against disease. Plasma cells that become cancerous are known as myeloma cells. A broad spectrum of different clinical signs may develop as myeloma cells proliferate, making this a difficult and challenging disease to diagnose and treat.

Currently reported feline myeloma-related disorders include:

  1. Myeloma
  2. Cutaneous extramedullary plasmacytoma (CEMP)
  3. Non-cutaneous extramedullary plasmacytoma (NCEMP)
  4. Solitary plasmacytoma of bone (SPB)
  5. Waldenströms (IgM) macroglobulinemia (WM)
  6. Immunoglobulin-secreting lymphoma
  7. Myeloma cell leukemia

Otto Kahler (1849-1893), a physician from Prague, is accredited with the first medical description of myeloma in humans.  Incidentally, the word myeloma is derived from two parts: myelo from the Greek word muelos meaning marrow, and oma, a Greek suffix commonly used to denote a tumor. The first description of myeloma in cats was not used until 1957 and was published by Holzworth & Meier from the Angel Memorial Animal Hospital in Boston. Many more reports on this condition now exist, but overall the myeloma-related disorders are relatively rare tumours in cats.

What Signs are seen with Myeloma-related Disorders?

cat myelomaSymptoms can vary tremendously within the same patient over time, as well as between patients. Clinical signs are dependent upon the location(s) the myeloma cell is proliferating in, as well as signs attributable to the excess production of antibodies by these cancerous myeloma cells. Furthermore, these tumors show differing patterns of clinical signs between different animal species.

Cats with myeloma commonly have anemia and this can contribute to the lethargy and weakness that may be seen. The cancerous myeloma cells typically produce immunoglobulins (monoclonal antibodies), which are often referred to as a paraprotein or M-protein. Filtration of the paraprotein by the kidneys leads to abnormal kidney function and even kidney failure. Excessive levels of paraprotein increase the “thickness” of the blood and result in hyperviscosity syndromes that may damage the eye (causing blindness), the nervous system (causing nerve or brain signs), the heart (cardiomyopathy), or in blood clotting (bleeding tendencies). The myeloma cells can congregate in clumps in various internal organs (e.g. in cats, the liver and/or spleen are commonly affected) or within skin, causing isolated tumors (or plasmacytomas), that can interfere with the normal function of these organs or the surrounding area. If the myeloma cells proliferate in the marrow – as happens in some cats, but is more common in human patients or dogs –  then destruction of bone can be seen (also known as osteolysis) causing bone pain or even fractures. Myeloma cells can also disturb the control of key body chemicals (such as calcium metabolism). Patients with myeloma can also be immunosuppressed and have a reduced ability to fight infections.

Treatment and Survival in Myeloma-related Disorders

cat laying downBefore commencing treatment, a complete diagnostic work-up is strongly recommended. The goal in treating multiple myeloma is to improve quality of life, relieve symptoms and pain if present, and to prolong survival. Complete cure has not been reported. Complete remission (meaning the alleviation of clinical signs) can be achieved. In one report, the majority of cats responded to combination chemotherapy and these cats had a median survival time of 12 months, which is not dissimilar to some reports for the treatment of standard lymphoma. Disease control is usually eventually complicated by a tendency for myeloma cells to become resistant to anti-cancer drugs.

What should I do if Myeloma is Suspected in my Pet?

Complete investigations for myeloma-related disorders are complex and may take several days. Ideally, referral to a veterinary oncologist in a multi-disciplinary specialist centre is in the best interests of the patient. Please draw the attention of your primary or referral veterinarian to the information available at and the clinical research being conducted at the Veterinary Myeloma Website.

About the author: Hilary Granson

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