Gammopathies occur in cats as a result of viral infections or cancer. The symptoms are vague and include weight loss, poor appetite, and lethargy. Some cases do recover, but the long-term outlook is poor with a 6 - 12 month survival time after diagnosis. 

The body defends itself against infection by producing antibodies, whose job it is to kill invading microorganisms. The building blocks of antibodies are called immunoglobulins. A gammopathy refers to a pathological condition where the body produces too much antibody and therefore an excess of immunoglobulins. This pathological (inappropriate) rise in immunoglobulins is known as a 'gammopathy'. 

The symptoms of gammopathies are vague and affected cats deteriorate gradually. Cancer-causing gammopathies are often based in the bone marrow, and the signs relate to poor health in general.

The cat is prone to infection as their immune system is weak. In rare cases, a cat may experience a fractured bone due to cancer in the bone marrow weakening its strength. Also, a gammopathy may thicken the blood, impairing circulation to organs such as the brain, causing seizures. 

Feline Infectious Peritonitis (FIP) is an infection that can trigger a gammopathy. In this case the signs will be those of FIP, as the gammopathy is a secondary effect. This includes a combination of:

Gammopathies can arise from a rise in a single (monoclonal) type of antibody, or from multiple (polyclonal) types of antibody

The most significant gammopathy to affect cats is 'multiple myeloma'. This is a cancer of the bone marrow which produces excessive amounts of B-cells. The trigger for development of this cancer is not known. 

FIP is another common cause of gammopathy as a secondary complication. FIP is caused by a mutation in the coronavirus which overstimulates the immune system and encourages spread of the FIP virus through the body.

Gammopathies do not have specific symptoms so a diagnosis is made when a sick cat is screened for problems. Basic blood profiles that look at protein levels in the blood, plus the numbers of red and white cells, may raise suspicion of a gammopathy. 

The vet will follow up with a specialized test called protein electrophoresis. This tests looks for spikes in immunoglobulin levels. The vet may also need to run tests to rule out similar problems such as lymphoma, vasculitis, and lupus. In addition, if the cat shows evidence of back or bone pain, radiographs may help to identify bone lesions. 

Thickening of the blood due to a gammopathy has an effect on blood flow and renal function. The vet may screen organ function and analyze fresh blood smears to troubleshoot for secondary problems such as hyperviscosity or lack of platelets. Only once they have a full picture of how the cat is affected, can a treatment plan be devised.

High doses of corticosteroids such as prednisolone are used to try and 'switch off' the production of immunoglobulins. In addition, the cat owner should be vigilant for signs of infection, since both the gammopathy and steroids reduce the body's ability to fight bugs. Prompt use of antibiotics may be required.

Urgent treatment of newly diagnosed cases with intravenous fluid therapy can help thin the blood and improve circulation to the brain and kidneys. 

In same cases, radiotherapy may be helpful if the cancer is accessible to radiation treatment, such as a bone neoplasia. This requires attendance at a specialist center and a general anesthetic for each treatment. 

The vet will also manage complications, such as high levels of calcium in the blood, by administering drugs such as pamidronate, a bisphosphonate. Regular blood screening is necessary in order to monitor treatment. 

Gammopathies associated with FIP are best treated by managing the cause, i.e. FIP infection. Whilst no cure is available, the use of interferon may help to extend life in some cases.

Survival times vary, but ultimately the long-term outlook is poor. An average survival time is around six months from the time of diagnosis, with 15 months in occasional cases. 

During this period, regular attendance for blood screening is necessary. This may be as often as weekly, in order to check the patient is stable. Relapses are common. 

The outlook for cats with FIP is poor, with no known cure available, the majority of affected cats deteriorate over weeks to months and require euthanasia on humane grounds.