What are Myeloma-related Disorders?
Myeloma is a type of cancer that affects certain white blood cells (cells of the immune system) called plasma cells. These are specialized lymphocytes, that in the healthy individual, are the cells responsible for producing antibodies to protect against disease.
Plasma cells that become cancerous are known as myeloma cells. A broad spectrum of symptoms may develop as myeloma cells take over, making these disorders challenging to diagnose and treat.
Currently reported feline myeloma-related disorders include:
- Cutaneous extramedullary plasmacytoma (CEMP)
- Non-cutaneous extramedullary plasmacytoma (NCEMP)
- Solitary plasmacytoma of bone (SPB)
- Waldenströms (IgM) macroglobulinemia (WM)
- Immunoglobulin-secreting lymphoma
- Myeloma cell leukemia
In the mid-19th century a physician from Prague was the first to descrive myeloma in humans. Today, many more reports on this condition now exist, but overall the myeloma-related disorders are relatively rare tumors in cats (as well as dogs). That said, on occasion they do occur.
What Signs are seen with Myeloma-related Disorders?
Symptoms can vary tremendously within the same patient over time, as well as between patients. Clinical signs are dependent upon the location(s) the myeloma cell is proliferating in, as well as signs attributable to the excess production of antibodies by these cancerous myeloma cells. Furthermore, these tumors show differing patterns of clinical signs between different animal species.
Cats with myeloma commonly have anemia and this can contribute to the lethargy and weakness that may be seen. The cancerous myeloma cells typically produce immunoglobulins (monoclonal antibodies), which are often referred to as a paraprotein or M-protein. Filtration of the paraprotein by the kidneys leads to abnormal kidney function and even kidney failure.
Excessive levels of a type of protein increases the “thickness” of the blood and result in hyperviscosity syndromes that may damage the eye (causing blindness), the nervous system (causing nerve or brain signs), the heart (cardiomyopathy), or in blood clotting (bleeding tendencies). The myeloma cells can congregate in clumps in various internal organs (e.g. in cats, the liver and/or spleen are commonly affected) or within skin, causing isolated tumors (or plasmacytomas), that can interfere with the normal function of these organs or the surrounding area.
If the myeloma cells proliferate in the marrow – as happens in some cats, but is more common in human patients or dogs – then destruction of bone can be seen (also known as osteolysis) causing bone pain or even fractures. Myeloma cells can also disturb the control of key body chemicals (such as calcium metabolism). Patients with myeloma can also be immunosuppressed and have a reduced ability to fight infections.
Treatment and Survival in Myeloma-related Disorders
Before commencing treatment, a complete diagnostic work-up is strongly recommended. The goal in treating multiple myeloma is to improve quality of life, relieve symptoms and pain if present, and to prolong survival. Complete cure in cats has not been reported. Complete remission (meaning the alleviation of clinical signs) can be achieved. In one report, the majority of cats responded to combination chemotherapy and these cats had a median survival time of 12 months.
What should I do if Myeloma is Suspected in my Pet?Complete investigations for myeloma-related disorders are complex and may take several days. Ideally, referral to a veterinary oncologist in a multi-disciplinary specialist center may be in the best interests of the patient.
However, your primary care veterinarian, depending on comfort, may begin by looking for some key things to help oint to myeloma:
1. elevated proteins in blood
2. Lesions in the skeleton visible in some feline x-rays
3. Abdominal ultrasound
4. A special urine test looking for abnormal proteins associated with Myeloma disease called Bence-Jones protein
5. Blood plasma electro-proteinphoresis – a special test sent to a reference laboratory that looks for abnormalities in the circulating white blood cells.
6. Complete Blood Count (CBC) and Chemistry as well as a urinalysis