"Boots" - Feline Addison's Disease - Case of the month
Boots is a 9-year-old domestic short haired cat who has a disease that is considered to be very rare in cats. Boots has hypoadrenocorticism (commonly known as Addison's disease). Click here for an in depth discussion on Addison's disease.
Boots was diagnosed back in 2001. It took a while to figure out what was wrong with him since there are only about 23 published cases of this disease in cats. The underlying cause of this disease in cats is still unknown but it is thought that it might be an autoimmune disease.
Addison's disease causes its symptoms when the body (specifically the adrenal gland) fails to produce enough hormones (glucocorticoids and mineralocorticoids). The symptoms a cat with this disease might show are very nonspecific and include; lethargy, lack of an appetite, weight loss, vomiting, diarrhea, weakness, dehydration, and a low temperature. A typical history may show a waxing and waning course of illness with the cat being sick and getting better repeatedly over a few weeks or months. Sometimes, if the disease is not diagnosed early, the cat may present to a Veterinarian in shock. Bloodwork may show some major abnormalities such as a low sodium and a high potassium level. Often the bloodwork abnormalities will mimic kidney failure. X-rays may show a small heart because the lack of the mineralocorticoid and glucocorticoid hormones.
This was an x-ray of Boots when he was diagnosed. The heart appears small and the lung fields and underperfused because of the Addison's disease.
The test to diagnose Addison's disease is called an ACTH stimulation test. When this test is performed, a blood sample is drawn for a baseline cortisol level and then a hormone called ACTH is given intravenously. One hour later, the cortisol level is taken again. In a cat with Addison's disease, both of these cortisol levels are very low. When Boots had this test performed, both the pre test and the post test cortisol levels were extremely low. This confirmed that he had Addison's disease.
Treatment of Addison's disease in the cat involves administering a source of the mineralocorticoid hormone and in some cases the glucocorticoid hormone. If the cat is sick when diagnosed, treatment usually also involves intravenous fluids and steroids. Boots did not appreciate taking pills every day so we started him on the injectable form of the mineralocorticoid called Percorten-V (Novartis Animal Health). This product is not labeled for use in cats by the FDA but appeared to be safe and effective. Boots required a once monthly injection for the rest of his life and periodic blood testing of his electrolytes (sodium and potassium levels) to ensure his dosage was correct.
Boots has cruised along and had been very healthy and his Addison's disease was under control for 6 years. In 2007, for an unknown reason, Boots had a relapse and had severe symptoms of his disease. He had a very low temperature, he was non responsive and almost comatose, his sodium level dropped significantly, and his potassium level increased significantly. This relapse occurred close to a holiday and we hypothesized that stress or a stressful event may have helped cause the relapse. His owner rushed him to the hospital and we treated him with steroids, intravenous fluids, another dose of his mineralocorticoid, and supportive care. He improved and was back to his normal self within 24 hours.
Boots is the case of the month for these reasons:
- He has done very well for years and had an amazing recovery when he relapsed.
- His owner is dedicated and brings him in faithfully every month for his injection.
- He has a very rare disease for a cat (and he helped Dr. Redden get published in a Veterinarian magazine when she wrote his case report!).
Boots relaxing at home....