Merck Manual

Please confirm that you are a health care professional

honeypot link
Pet Owner Version

Muscle Disorders in Cats


Joseph Harari

, MS, DVM, DACVS, Veterinary Surgical Specialists, Spokane, WA

Reviewed/Revised Aug 2018 | Modified Oct 2022

Myopathies are diseases that primarily cause damage to muscles or muscle tissues. They may be present at birth (congenital) or occur due to nutritional imbalances, muscle injury, ingestion of a poisonous substance, cancer, metabolic disturbances, and inflammation. Myositides are diseases that produce a mainly inflammatory reaction in muscle. Common causes include infections, parasitic diseases, and immune-mediated conditions. Sometimes, the cause is unknown.

Yellow Fat Disease (Steatitis)

Yellow fat disease is a condition in which inflammation of the fatty tissue (which develops a yellow tinge) occurs. It is thought that an excess of unsaturated fatty acids in the food, combined with a deficiency of vitamin E or other antioxidants, causes this condition. Most known cases have involved animals whose diet consists partially or completely of fish or fish byproducts. Fish are rich in fatty acids.

Affected cats are usually young and may be male or female. They are frequently obese. Early signs may include a dull hair coat or dry skin. Cats often become lethargic and lose agility. The back or abdomen becomes very tender. In advanced cases, even a light touch can cause pain. Lumpy deposits of fat under the skin may be seen. Fever is always present, and loss of appetite is common.

The cat’s diet must be changed to exclude the source of excess fat. In addition, supplementing the diet with vitamin E in an appropriate form is usually recommended. Antibiotics are not helpful, as the condition is not bacterial. Because the condition is quite painful, affected cats are given prescription pain medications and should be handled as little as possible.

Hypokalemic Polymyopathy

Hypokalemic polymyopathy of cats is a muscle weakness disorder. It affects the whole body and is caused by potassium deficiency. Signs include generalized weakness, bending forward of the neck, abnormal gait, persistent loss of appetite, and muscle pain. Blood and urine tests are used to confirm the diagnosis. The condition is treatable with dietary potassium supplements, given as recommended by a veterinarian. The outlook for recovery is excellent if the condition is diagnosed and treated quickly.

Malignant Hyperthermia

Malignant hyperthermia is a disorder of skeletal muscle usually brought on by certain types of inhaled anesthesia and stress. It is characterized by an abnormal increase in metabolic rate and body temperature. Although the condition is most common in pigs, it also occurs in some cats.

Signs include rapid heartbeat, increased breathing rate, fever, muscle tightness and rigidity, and heart and lung failure. Signs develop between 5 and 30 minutes after exposure to the anesthetic agent. Treatment requires immediately stopping the anesthesia and administering oxygen. Fluid injections, corticosteroids, ice packs, and muscle relaxants are also used. The outlook is poor in severe cases.

Muscle Tumors

Skeletal muscle tumors can be benign or cancerous Cancer and Tumors (malignant). Malignant tumors can spread and invade nearby muscle. They can also spread to other parts of the body. Signs include localized swelling and lameness. The diagnosis is confirmed by taking a small tissue sample called a biopsy. The tumor generally must be surgically removed or the limb amputated. Chemotherapy and radiation may be used depending on the type of tumor.

For More Information

quiz link

Test your knowledge

Take a Quiz!