What is systemic lupus?
Systemic lupus is a rare feline autoimmune disease caused by abnormal regulation of the immune system. An affected 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 a definitive breed predisposition has not been established, Siamese, Himalayan, and Persian cats appear to be more likely than other breeds to develop systemic lupus.
"...Siamese, Himalayan, and Persian cats appear to be more likely than other breeds to develop systemic lupus."
What are the clinical signs of systemic lupus?
Systemic 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, and paws, or can be generalized across the body.
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 a fever that does not respond to antibiotics, lameness, joint swelling and/or pain, stiff gait, decreased appetite, lethargy (decreased energy), and oral ulcerations.
How is systemic lupus diagnosed?
There is no single test to diagnose systemic lupus, making it a challenge for veterinarians to diagnose. Most veterinarians use the American College of Rheumatology’s “Eleven Criteria of Lupus” to establish a diagnosis of systemic lupus. In human patients, four of these eleven criteria must be present in order to arrive at a diagnosis. In veterinary patients, just three of these criteria can suggest a likelihood of the disease.
"There is no single test to diagnose systemic lupus, making it a challenge for veterinarians to diagnose."
Skin biopsies are frequently performed in the early evaluation of systemic 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. In cats with systemic lupus, characteristic changes within the skin observed by a pathologist can 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 count), 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.
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 (Atopica™), chlorambucil, cyclophosphamide, or mycophenolate mofetil (MMF) may be required.
"Due to the possibility of a genetic component of the disease, affected cats should not be bred."
Cats with systemic lupus should be kept indoors, as exposure to sunlight will worsen the severity of the skin lesions. Due to the possibility of a genetic component of the disease, affected cats should not be bred.
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, requiring lifelong frequent monitoring. Others cannot have their symptoms controlled, even with appropriate medical therapy.
