Systemic Lupus in Cats
What is systemic lupus?
Systemic lupus is a rare feline autoimmune disease, caused by abnormal regulation of the immune system. In this condition, the cat’s immune system recognizes the body’s own cells as foreign. The immune system forms antibodies against tissues in the body, directly attacking the body’s own cells and depositing antibodies throughout the body’s tissues.
Although no definitive breed predisposition has been established, Siamese cats appear to be more likely than other breeds to develop systemic lupus.
What are the clinical signs of systemic lupus?
"Approximately 60% of affected cats present with skin lesions."
Lupus can affect many body functions and systems, depending on the specific immune dysregulation that occurs.
Approximately 60% of affected cats present with skin lesions. These lesions may appear as reddening of the skin, ulcers, or erosions caused by the immune system’s attack on the skin. Most often, these skin lesions are noted on the face, ears, paws, or can be generalized across the body/trunk.
Affected cats also show signs of systemic illness, due to the effects of lupus on other body systems. Signs may appear suddenly, or they may be chronic. In some cats, signs wax and wane over time.
Signs of systemic illness include:
Fevers that do not respond to antibiotic therapy
Lameness, often described as “shifting-leg lameness” (involving different legs at different points in time)
Swelling or pain in the joints
Stiffness when moving
Lethargy or decreased activity
How is systemic lupus diagnosed?
There is no single test that can be relied upon to establish a diagnosis of systemic lupus, making lupus a challenge for veterinarians to diagnose.
"Skin biopsies are frequently performed in the early evaluation of lupus."
Most veterinarians use the American College of Rheumatology’s “Eleven Criteria of Lupus” to establish a diagnosis of lupus. In human patients, four of these eleven criteria must be present in order to arrive at a diagnosis. In veterinary patients, even three of these criteria can suggest a likelihood of lupus.
The eleven criteria are:
Butterfly shaped facial rash
Discoid rash: raised red patches on the skin
Photosensitivity: skin rash in response to sunlight
Mouth or nose ulcers
Inflammation in two or more joints
Inflammation of the lining around the heart or lungs
Neurologic disorders, including seizures
Kidney function abnormalities
Blood disorders, including anemia, low white blood cell count, or low platelet count
Antibodies against certain components of the blood and cells
Antinuclear antibodies (ANA)
Skin biopsies are frequently performed in the early evaluation of lupus. Your veterinarian will use sedation and a local anesthetic to obtain a small skin sample from an affected area of your cat’s body. This sample will be sent to a laboratory, where it will be specially prepared and then examined under a microscope by a pathologist. In cats with systemic lupus, characteristic changes are observed within the skin that help with the diagnosis. The pathologist may also use specialized techniques to assess for the presence of antibody deposits in the skin.
Your veterinarian will also perform bloodwork to assess your cat’s cell counts and organ function. Cats with systemic lupus often have anemia (low red blood cell counts), as well as decreased numbers of platelets and white blood cells.
An antinuclear antibody (ANA) test may also be performed if your veterinarian suspects systemic lupus. This test assesses the presence of antibodies against the body’s own cells, which can be used to support a diagnosis of lupus.
How is systemic lupus treated?
Treatment of systemic lupus relies on suppressing the overactive immune system. Most frequently, this immunosuppression is performed with corticosteroid drugs, such as prednisolone or dexamethasone. In more severe cases, additional immunosuppressive drugs such as cyclosporine, chlorambucil, or mycophenolate mofetil (MMF) may be required.
"Treatment of systemic lupus relies on suppressing the overactive immune system."
Affected cats should be kept indoors, as exposure to sunlight will worsen the severity of the skin lesions. Also, these cats should not be bred, due to the possibility of a genetic component of the disease.
What is the prognosis for systemic lupus?
Systemic lupus is a serious condition and the prognosis, even with treatment, is generally viewed as guarded. Some cats will survive with lifelong immunosuppressive treatments, but others cannot have their signs controlled even with appropriate medical therapy.
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