Multiple Myeloma in Dogs
Plasma cells are specialized white-blood cells, lymphocytes that have been altered to produce immunoglobulin, an immune protein or antibody necessary for fighting disease. Multiple myeloma is an uncommon cancer that is derived from a clonal population of cancerous (malignant) plasma cells in the bone marrow.
Three of four defining features must be present for a diagnosis of multiple myeloma: immune protein from a single clone of cells (known as a monoclonal gammopathy), seen as a spike in the gamma region of a protein analysis of the blood (known as a protein electrophoresis); cancerous plasma cells or a high number of plasma cells in the bone marrow (known as plasmacytosis); destruction of areas of bone (known as lytic bone lesions); and a particular type of protein found in the urine (known as Bence Jones [light-chain] proteinuria).
Multiple myeloma occurs in German shepherd dogs and other purebred dogs more often than mixed-breed dogs, and primarily in middle-aged or older dogs (6-13 years).
Symptoms and Types
Multiple myeloma is attributed to bone infiltration and destruction of the bone, effects of the proteins that have been produced by the tumor (such as increased protein in the blood leading to sludging of the blood and kidney damage), and infiltration of organ(s) by cancerous cells. Symptoms depend on the location and extent of the disease.
- Weakness, sluggishness (lethargy)
- Lameness is seen in 47 percent of affected dogs
- Bone pain and weakness is seen in 60 percent of affected dogs, with concurrent destruction of areas of bone
- Partial paralysis
- Dementia with generalized discomfort or uneasiness seen in 11 percent of affected dogs
- Labored breathing
- Increased thirst and increased urination is seen in 25 percent of affected dogs, with increased levels of calcium in the blood or kidney dysfunction
- Urinary incontinence
- Enlarged liver and spleen
- Excessive bleeding from needle punctures to collect blood or to administer intravenous medications and/or fluids
- Bleeding involving the gastrointestinal tract
- Bleeding - especially from the nose or mucous membranes (the moist tissues of the mouth, eyes, and other areas of the body) is seen in 36 percent of affected dogs.
- Bleeding in the back part of the eye and blindness, retinal hemorrhage, or dilated retinal vessels is seen in 35 percent of affected dogs
- Pale gums and other moist tissues of the body (mucous membranes)
- Detached retina
- Inflammation of the front part of the eye including the iris
- Coma (rare)
You will need to give a thorough history of your dog’s health, and onset of symptoms. The history you provide may give your veterinarian clues as to which organs are causing secondary symptoms. Along with a thorough physical examination, your veterinarian will also conduct a thorough ophthalmological examination on your dog, if the eyes are showing symptoms of a diseased state.
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. To do that, your doctor will conduct a complete blood profile, including a chemical blood profile, a complete blood count, and a urinalysis. Diagnostic imaging will include X-rays of the vertebra and limbs to look for bone lesions, and ultrasound to examine the internal organs.
Your veterinarian may need to refer you to a veterinary oncologist for the latest information regarding treatment of this disease. Your dog may be hospitalized if there are high levels of urea - waste products and calcium in the blood. Also, if there is a bleeding disorder, or a significant bacterial infection, hospitalization may be required. A blood-cleansing procedure may be used, or blood may be withdrawn and replaced with an equal volume of fluids.
If possible, radiation therapy may be used on isolated areas, with the goal of curing the disease, or only to control signs and improve your dog’s condition. If there is a concurrent bacterial infection, it will be treated aggressively with antibiotics.
If your dog is being treated with radiation or chemical therapy, it will also need to be guarded against opportunistic infections that can result from the expected lowered immune response (known as immune compromised – a result of the treatment that is used to stop the growth of cancerous cells in the body). You will need to take care to prevent bacterial infections from occurring, such as those caused by puncture wounds from dog or cat fights. Dietary changes will be necessary if your dog is in kidney failure. Affected areas that are nonresponsive to chemotherapy, or single, solitary lesions may be removed surgically.
Living and Management
Your veterinarian will want to do a complete blood count and platelet count weekly for at least four weeks to assess bone-marrow response to the chemotherapeutic drugs. Blood tests with abnormal results will be repeated monthly to evaluate response to the treatment.
Protein analyses of the blood will be done monthly for several months until normal protein patterns are obtained. Once protein patterns have stabilized, monitoring will be periodically performed for signs of relapse. Abnormal skeletal X-rays should be repeated monthly every other month until they appear normal, and to evaluate your dog’s response to treatment.
Chemotherapy is intended to improve your dog’s condition, not to cure the multiple myeloma, but long remissions are possible. Relapse is an expected occurrence. The drugs that are being used will determine the side effects. Your veterinarian will go over what to expect, based on the types of drugs that are prescribed for treatment. Most patients develop mild low white-blood cell counts (leukopenia) during chemotherapy.