The immune system in a cat’s body has a committed task. It is a complex interconnected system of white blood cells, antibodies and other substances that are released to combat infections and eliminate foreign proteins. On recognition of a foreign invasion, the system releases antibodies which chemically bind with antigens to destroy them.
The important part of the immune system is that it is supposed to recognize foreign substances and respond immediately to destroy them. Unfortunately, it does not always happen like this. Certain disorders cause the controlling mechanism of the immune system to fail, and it produces antibodies that attack the body’s own tissues. These are known as auto-antibodies. The resultant disease is known as an autoimmune disease. Even though it is known that an autoimmune disease is caused by production of these auto-antibodies, the underlying causes are complicated and not thoroughly understood.
Symptoms of autoimmune diseases vary depending upon the organ or system that has been affected. In certain cases, multiple organs and body systems are affected. Autoimmune diseases occur in both cats and dogs, producing relatively similar symptoms.
The autoimmune disease of the blood in cats is rare and often secondary to leukemia. The antibodies disrupt the body’s own red blood cells causing hemolysis, a condition known as autoimmune hemolytic anemia. It may cause jaundice, lethargy, enlargement of lymph nodes and ulcerations in ears, nose, tail and feet. It is often accompanied with a substantial fall in platelet count. Hemolysis can also be drug induced, so a proper diagnosis is a must before proceeding with treatment.
If the cat is showing signs of muscle weakness, difficulty in eating and swallowing, and regurgitation, there are chances that auto-antibodies are attacking the acetylcholine receptors on the muscles. This can be a sign of a chronic progressive disease characterized by chronic fatigue and muscular weakness, especially in the face and neck, known as Myasthenia gravis.
Another musculoskeletal autoimmune disease in cats may occur in the form of rheumatoid arthritis. Rheumatoid arthritis causes extreme disability in the shape of lameness and stiff joints. In its extreme manifestation, a cessation of joint movement can also occur. Where the skin is affected, it causes ulceration in the mucous membranes of the skin, serum discharging lesions, crusts over the ulcers, itchiness and alopecia.
Autoimmune disease may affect multiple organs at the same time. Multiple organ autoimmune disease is common and makes diagnosis extremely difficult. The name itself presupposes the presence of multiple symptoms that can be confusing at times, even for the expert veterinarian. There are indications that feline liver disease, such as chronic active hepatitis may have a connection with a malfunctioning immune system.
The complement system in the body is a series of proteins like the antibodies and is named based on the fact that its function complements the antibodies. Complement proteins are manufactured in the liver and sometimes liver disease in cats and dogs may be a precursor of an immune mediated disease. Consulting your veterinarian is advisable when you see symptoms of liver disease in cats and dogs.
Prognosis of most of the autoimmune diseases is generally poor if not treated in the earlier stages. Those affecting the skin usually go into remission on treatment with drugs. Autoimmune hemolytic anemia and autoimmune thrombocytopenia (fall in platelet count in blood) requires aggressive treatment. Myasthenia gravis, the musculoskeletal disorder, has a guarded prognosis with an underlying risk of death.