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Multiple Myeloma in Dogs

Posted April 24, 2015 in Dog Diseases & Conditions A-Z

Multiple myeloma is a cancerous process that people and dogs have in common. This disease is also referred to as myeloma and plasma cell myeloma. Although not considered curable, this relatively uncommon canine disease can be successfully treated.

Woman petting sad dogWhat is multiple myeloma?

  • Starting in lymphocytes—Multiple myeloma cells originate from lymphocytes, a normal type of white blood cell that resides in the bone marrow.
  • Some Lymphocytes become plasma cells—These lymphocytes differentiate into a variety of different types of cells, one of which is the plasma cell, an important component of the body’s immune system.
  • Sometimes, there are too many plasma cells—In cases of multiple myeloma, plasma cells developing within the bone marrow undergo a malignant transformation, and way too many plasma cells are manufactured.
  • This means less room for other cells—This results in a “crowding out” of the normal bone marrow production of infection fighting white blood cells, oxygen carrying red blood cells and platelets (the cells responsible for controlling bleeding in the body). Myeloma patients often have dangerously low numbers of these normal cells within their bloodstream.
  • The malignant cells spread—Once released from the bone marrow, the malignant plasma cells often spread to other sites. Their favorite place to set up housekeeping is within bones where the damage caused by the cancer cells can create significant pain for the patient.
  • Too many plasma cells lead to thick blood—Plasma cells produce proteins called immunoglobulins that are the foot soldiers of the immune system. An overabundance of plasma cells, as is the case with multiple myeloma, translates into an overabundance of immunoglobulin found in the bloodstream. This immunuoglobulin alters the normal thickness of the blood, transforming its normal water-like consistency to that of syrup. This change wreaks havoc within smaller blood vessels where the blood sludges and causes damage to the tissues. This is referred to as hyperviscosity syndrome and can be life threatening, particularly if the brain is affected.

Cause of multiple myeloma in dogs
According to a study found on PubMed.gov, multiple myeloma in people has been associated with exposure to toxic chemicals present in tobacco smoke and emissions from petroleum refinery waste dumps and industrial operations.

The cause of multiple myeloma in companion animals is unknown, and there is no breed or sex predilection. Middle aged to older dogs and cats are most commonly affected.

Symptoms of multiple myeloma in dogs
The major symptoms associated with multiple myeloma are caused by the spread of cancer cells, hyperviscosity syndrome (thick blood), and too few normal cells within the bone marrow (see explanations above). Additionally, some dogs and cats with myeloma develop hypercalcemia, a higher than normal level of calcium in the bloodstream. This hypercalcemia can produce a number of serious consequences over time, the most significant of which is kidney failure.

Because multiple myeloma cells can wreak havoc in so many ways, the symptoms associated with this disease vary from patient to patient. Most commonly reported symptoms include:

  • Lethargy
  • Weakness
  • Loss of appetite
  • Lameness and/or bone pain (caused by the spread of cancer cells)
  • Unexplained bleeding
  • Loss of vision
  • Abrupt onset of neurological symptoms or seizures
  • Increased thirst and urine output
Related symptoms: 

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Nancy has more than 30 years of experience in the veterinary industry and is a board-certified veterinary specialist in internal medicine as well as a valued member of IDEXX’s Pet Health Network team since 2014.