Multiple Myeloma in Cats

Multiple myeloma is a type of cancer that is relatively uncommon in cats, though is more prevalent in dogs and humans. It most often occurs in middle-aged or older cats (typically 6-13 years of age). It is characterized by the abnormal growth of plasma cells, which are a type of white blood cell. While the exact cause of multiple myeloma is unknown, certain risk factors, such as genetic predisposition and exposure to certain chemicals, are hypothesized as potential causes. This article will present a comprehensive overview of multiple myeloma in cats, helping you understand what it is, its types, symptoms, diagnostic procedures, treatment options, and prognosis.

What is Multiple Myeloma in Cats?

Feline multiple myeloma is a form of cancer that originates in the plasma cells in the bone marrow. Plasma cells are a type of white blood cell responsible for producing antibodies that help fight infection. In multiple myeloma, these cells become abnormal and proliferate uncontrollably, leading to various systemic effects and complications.

Multiple myeloma is a disease that can lead to elevated levels of a certain protein circulating in the bloodstream called immunoglobulins. While cats have many types of immunoglobulins, in multiple myeloma only one type of immunoglobulin will be produced excessively. This is called a monoclonal gammopathy. Multiple myeloma can also cause the infiltration of cancerous plasma cells into organs such as the liver and the spleen, resulting in bone disease, bleeding tendencies, hyperviscosity syndrome (thickening of the blood), immunodeficiency (increased susceptibility to infection), low blood cell counts, and heart failure.

The specific cause of multiple myeloma in cats is unknown but some hypothesize that it may develop from viral infections, chronic immune stimulation, and/or exposure to carcinogens.

Signs and Symptoms of Multiple Myeloma in Cats

The symptoms of multiple myeloma in cats can be varied and sometimes subtle, often related to the organs affected by the abnormal plasma cells and the high levels of immunoglobulins in the blood.

Common signs of feline multiple myeloma include:

• Lethargy and weakness
• Loss of appetite and weight loss
• Increased thirst and urination from an abnormal elevation of calcium caused by the cancer
• Lameness or pain from the bones (rare in cats)
• Plasmacytomas, solitary tumors that form in a variety of locations including the skin, mouth, ears or GI tract
• Bleeding or unusual bruising
• Anemia, low white blood cell counts, and low platelet counts can occur
• Kidney problems, which may manifest as vomiting or changes in urination habits
• Unexplained infections

Identifying Feline Multiple Myeloma

For a diagnosis of multiple myeloma, at least three features must be present, including plasma cell infiltrate in an organ(s):

1. Monoclonal gammopathy is the excess of an immune protein from a single clone of cells. Detecting monoclonal gammopathy is done through a blood test called protein electrophoresis.
2. Plasmacytosis is characterized by a high number of plasma cells (>10-20%) in the bone marrow. It is confirmed through bone marrow aspirate and is a defining characteristic of multiple myeloma. Plasmacytosis can damage and reduce the production of red blood cells (anemia), white blood cells (leucopenia), and platelets (thrombocytopenia).
3. Lytic bone lesions result from multiple myeloma, causing bone destruction. These lesions may lead to pain, lameness, fever, lethargy, anorexia, weight loss, and fractures due to weakened bones. X-rays and CTs are commonly used to detect them.
4. Proteinuria in multiple myeloma is caused by Bence-Jones proteins, a specific type of light-chain protein. These proteins can be found in the urine when there is an abnormally high number of malignant plasma cells.
5. Elevation in the calcium. This can be diagnosed on a blood test called a chemistry profile.
6. Malignant plasma cells infiltrate other organs such as the liver, spleen, and lymph nodes. This can be diagnosed by ultrasound-guided aspiration of affected organs.

Diagnosing & Staging Multiple Myeloma in Cats

Diagnosing a cat suspected of having multiple myeloma requires a thorough approach, as symptoms can vary widely within the cat itself as well as from one cat to another. Symptoms are often similar to other conditions, even the cancer called lymphoma, so your veterinarian will likely take a close look at your cat’s health history, and current symptoms and recommend a series of tests, including:

• A complete blood count (CBC) to detect any irregularities in red blood cells, white blood cells, or platelets. It provides valuable insights into the overall health and functioning of the blood.
• Chemistry profile to evaluate various aspects of health including total protein levels, liver function, kidney function, calcium level, and more
• Urinalysis to check the cat’s kidney function
• Bence-Jones assay to assess your cat’s urine for light chain proteins
• Protein electrophoresis examines the elevation in proteins and determines if it is due to monoclonal gammopathy (one specific band or type) or from polyclonal gammopathy (many bands or types)
• Bone marrow aspirate will be conducted if your veterinarian thinks it’s necessary to examine the percentage of plasma cells within the bone marrow
• 3-view Chest X-rays and/or CT Scan will reveal any bony lesions (which are rare in cats)
• Abdominal ultrasound with aspiration cytology looks at your cat’s internal organs and reveals any signs of malignancy or spread

Once diagnosed, the disease is staged based on various factors such as the number of malignant plasma cells present in the bone marrow, and the extent of their spread in the body. The staging process helps your veterinarian determine the severity of the disease, tailor treatment plans, and provide a more accurate prognosis for your furry family member.

Treatment Options for Cats with Multiple Myeloma

Treatment for multiple myeloma in cats is primarily aimed at controlling the disease and alleviating symptoms, as a cure is often not possible. Treatment options may include:

• Chemotherapy: Oral drugs like melphalan or intravenous drugs are commonly used to kill cancer cells and slow the progression of the disease
• Corticosteroids: Drugs like prednisolone can help reduce the cancer burden and help to lower a high calcium level
• Surgery can help remove solitary plasmacytomas
• Radiation therapy can be used to help reduce bone pain, to target local areas of disease, or for cats with solitary plasmacytomas
• Supportive Care: This includes treatments aimed at managing symptoms, such as pain medication, fluids to address dehydration, and nutritional support

It’s important to discuss the potential benefits and side effects of each treatment option with your veterinarian to determine the best course of action for your cat and to provide your cat with the best quality of life.

Prognosis for Cats with Multiple Myeloma

Multiple myeloma in cats is not curable, so treatment aims to extend the cat’s life and improve any symptoms. The prognosis for cats with multiple myeloma varies depending on several factors, including the stage of the disease, the overall health of the cat, and how well they respond to treatment. While some cats may respond well to therapy and enjoy a good quality of life for some time, the long-term outlook is generally guarded to poor. Regular follow-up and monitoring are crucial to adjusting treatment plans and ensuring the best possible outcome for your cat.

Multiple myeloma in cats is a complex and challenging disease, but understanding its aspects can empower you to make informed decisions about your cat’s care. With advances in veterinary medicine and a compassionate approach, you can provide your furry friend with the love and support they need during this journey. Remember, you’re not alone, and your dedication makes a significant difference in your cat’s life.

Coping with a cancer diagnosis in a pet is never easy. As a dedicated pet parent, your role in providing love and care, coupled with the expertise of your veterinary team, is invaluable. Stay informed, ask questions, and consider support groups or counseling to help navigate this challenging time. If you have questions about your cat’s multiple myeloma diagnosis, please feel free to contact our Pet Advocate Team. It’s a free service to help pet parents navigate any cancer diagnosis. Our Pet Advocates can be reached at 833-PET-HERO or by calling 833-738-4376.