Myeloma

Myeloma is among the more serious cancer diagnoses a dog can receive – and simultaneously one of the less well-known. It originates from plasma cells in the bone marrow, i.e. precisely those cells that normally produce antibodies to fight off infections. The term multiple myeloma arises because the disease usually does not remain confined to a single site, but affects multiple areas of the bone marrow and bones. The malignant plasma cells produce abnormal antibodies that can harm the immune system and the entire body. In dogs, multiple myeloma is rare – but when it occurs, it is severe.

What is Myeloma?

Multiple myeloma is a malignant cancer that originates directly in the bone marrow – specifically in the plasma cells, which normally take on antibody production there. In the diseased state, these cells divide uncontrollably, form tumours and undermine several vital systems at once: the bone structure becomes more brittle, the kidneys come under pressure, the immune system loses its effectiveness, and the circulatory system can also be impaired. In short: myeloma deeply affects the dog’s biology.

Causes of Myeloma in Dogs

Why a dog develops myeloma cannot yet be said with certainty. Research assumes that both genetic and environmental factors play together. The following risk factors are discussed:

• Genetic predisposition: Certain breeds seem to be affected more frequently – including German Shepherds, Labrador Retrievers and Golden Retrievers.
• Immunodeficiency: A persistently weakened immune system – for example due to chronic infections or autoimmune diseases – could favour the development of myeloma.
• Exposure to environmental toxins: Contact with certain chemical substances or radiation is considered a possible risk factor for various forms of cancer, including myeloma.
• Age: The disease affects almost exclusively older dogs – most patients are older than 8 years at diagnosis.

Symptoms of Myeloma in Dogs

The insidious thing about myeloma: the symptoms are varied and cannot be confined to a single area, because the abnormal plasma cells burden bones, the immune system, kidneys and other organs. Typical signs that owners should watch out for:

• Bone pain: Affected dogs often show pain in certain places, which can manifest as lameness or as a defensive reaction when touched. The weakened bone structure makes fractures more likely.
• Weakness and fatigue: Many dogs appear lethargic, lose their stamina and tire faster than usual even with short exertions.
• Weight loss: Unexplained weight loss is a common accompanying sign – the body works under high stress, which consumes energy.
• Increased susceptibility to infection: Because myeloma weakens the immune system, infections keep recurring or respond less well to treatments than usual.
• Increased thirst and frequent urination: Myeloma-induced kidney damage can lead to significantly increased drinking (polydipsia) and frequent urination (polyuria).
• Tendency to bleed: The disturbed production of normal blood components can lower the platelet count, which impairs coagulation and increases the risk of bleeding.
• Anaemia: From the same cause, a blood deficiency (anaemia) can develop – recognisable by weakness and pale mucous membranes.
• Eye symptoms: In some cases, dogs show eye problems such as haemorrhages or visual disturbances, triggered by bleeding or tumour growth behind the eyes.

Diagnosis of Myeloma in Dogs

A myeloma cannot be proven by a single test – it requires a bundle of clinical examinations and diagnostic procedures:

Blood tests:

• In the blood, signs of anaemia, kidney failure or increased calcium levels (hypercalcaemia) may appear – all typical accompanying findings in myeloma.
• The blood picture can also reveal changes in white blood cells and platelets.

Blood electrophoresis:

• This test detects abnormal antibodies (paraproteins) in the blood, which originate from the degenerated plasma cells – an important indication of myeloma.

X-rays:

• X-ray images make bone damage or lesions visible that myeloma leaves behind. Affected bones often appear pitted or thinned in the image.

Bone marrow biopsy:

• The definitive diagnosis almost always requires a bone marrow biopsy: a sample is taken and examined for abnormal plasma cells.

Urine tests:

• Bence-Jones proteins can be detected in the urine – these are abnormal antibody fragments that the kidneys frequently excrete in myeloma patients.

Treatment of Myeloma in Dogs

In the vast majority of cases, multiple myeloma in dogs is not curable. Treatment therefore pursues realistic goals: to slow the progression of the disease, relieve pain and enable the dog to have a good life for as long as possible. The following approaches are used:

• Chemotherapy: It is considered standard treatment. The combination of Melphalan and Prednisone is the most common – it slows the growth of cancer cells and reduces the number of abnormal plasma cells. If the response is insufficient, Cyclophosphamide or Vincristine are sometimes also used.
• Radiation therapy: If myeloma occurs locally or causes severe bone pain, radiation therapy can reduce the tumour mass and significantly reduce the pain.
• Pain management: Non-steroidal anti-inflammatory drugs (NSAIDs) or Opiates can relieve the bone pain caused by myeloma – an often underestimated but central part of therapy.
• Treatment of hypercalcaemia: Elevated calcium levels in the blood are common with myeloma and can lead to lethargy, kidney problems, and further complications. Fluid therapy and medications such as bisphosphonates help lower calcium levels.
• Supportive care: This includes adapted nutrition – for example, kidney-friendly diets –, targeted immune support, and regular veterinary check-ups to monitor disease progression.

Prognosis

The outcome for a dog with multiple myeloma depends heavily on how early the disease is detected and how well it responds to therapy. Chemotherapy started early can extend survival time and noticeably improve quality of life. Without treatment, myeloma usually progresses rapidly and leads to serious complications – kidney failure, bone fractures, and pronounced immunosuppression are the most common.

With targeted therapy, many affected dogs achieve a survival time of one to two years, sometimes longer – depending on the individual response to treatment and whether comorbidities complicate the picture.