Multiple Myeloma in Dogs

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. They develop from a type of white blood cell called a B cell. Plasma cells produce antibodies, which are used by the body to fight infections. In patients that develop multiple myeloma, these plasma cells multiply uncontrollably

Multiple myeloma is an uncommon disease in dogs, accounting for less than 8% of all hematopoietic tumors in dogs.

Multiple myelomas have been described most commonly in dogs, humans, and cats. They account for less than 1% of all malignant canine tumors, and 8% of all malignant hematopoietic tumors in dogs, and 3.6% of all primary and secondary bone tumors diagnosed by biopsy.

No breed or sex predilections exist, and older dogs are most commonly affected. Although certain breeds seem to be more susceptible to developing plasma cell tumors including Airedale Terriers, Cocker Spaniels, Kerry Blue Terriers, Scottish Terrier, and Standard Poodles.

Symptoms for multiple myeloma resemble those of several other diseases. Your veterinarian will need to rule out a number of other possibilities for the symptoms, such as infections, other types of tumors, and immune-mediated illnesses.

Causes of Multiple Myeloma in Dogs

The cause of multiple myeloma in companion animals is unknown. In people, plasma cell diseases are associated with working in the agricultural industry, exposure to petroleum products, and chronic exposure to an antigen stimulus.

Signs and Symptoms of Multiple Myeloma in Dogs

Affected dogs can exhibit signs of lethargy, weakness, lameness, bone pain, hemorrhage, gingival bleeding, and epistaxis), polyuria / polydypsia, and/or neurologic deficits. Other presenting signs of disease may include hypertension, ophthalmic abnormalities, retinal hemorrhages, and retinal detachment), neurologic dysfunction (including seizures), organomegaly, and suggestion of multiple organ failure.

Diagnosis

This cancer can be difficult to diagnose. On radiographs (x-rays), your veterinarian may note an area of osteolysis (decreased bony mass) often within the vertebra or ribs. This bony change, however, can be found in any bone. Also, your dog may have a high level of circulating globulins or proteins in their bloodwork.

Another typical abnormality seen in patients with this type of cancer is excessive urine protein, called bence jones proteinuria. A bone marrow biopsy aspirate can be used to support a diagnosis. Depending on physical examination and preliminary diagnostic tests, your oncologist may recommend further diagnostic tests such as images or biopsies. Traditionally, 3 out of the 4 positive diagnostic tests above are needed to confirm this cancer.

Treatment of Multiple Myeloma in Dogs

Because multiple myeloma is a systemic disease of plasma cells, it is generally treated with chemotherapy. Once chemotherapy is initiated, signs associated with the tumor tend to resolve. Multiple myeloma tends to recur, and your pet may exhibit signs while being treated or after chemotherapy is completed. If this does occur, other chemotherapy treatments may be pursued.

Aggressive fluid therapy is employed for renal failure and hypercalcemia; as long-term treatment is used to ensure an adequate hydration to the dog.

Multiple myeloma in dogs is also typically is treated with melphalan. A daily melphalan dosing schedule reportedly is well tolerated and associated with favorable outcome