If your veterinarian suspects that your cat may have a muscular disease or disorder, he will perform a blood chemistry panel to check the levels of specific muscle enzymes. In addition, he will perform a complete blood count, urinalysis and x-rays to assist in the diagnosis.
Muscle enzymes include creatine kinase, creatine phosphokinase, aldolase, lactate dehydrogenase and aspartate aminotransferase. These enzymes are found in all the muscles of a cat's body, including the heart and lungs.
Myositis is a localized or generalized inflammation of muscle caused by parasites, immune disorders, drug toxicity and cancer. Myositis causes the enzyme creatine kinase to be highly elevated in cats.
Polymyositis is an immune-mediated disease that causes general weakness of muscles throughout the cat's body. This disease causes elevated serum levels of creatine kinase and aldolase.
Hypokalemic polymyopathy occurs when the potassium level in the cat's body falls well below normal levels. Since this disease can affect the muscles of the heart and lungs, severe hypokalemia can be life threatening. Hypokalemic polymyopathy causes an extremely elevated level of creatine kinase.
The heart is a large muscle, and diseases and disorders of the heart such as cardiomyopathy and congestive heart failure can cause elevated levels of creatine phosphokinase, creatine kinase and aspartate aminotransferase.