Animals that contract viral infections in the womb may be born with diseased or deformed musculoskeletal systems. Abnormalities may also be congenital (present at birth) if a mother eats toxic plants at certain stages of the pregnancy. Some inherited (genetic) conditions affecting the musculoskeletal system may be neurologic in origin.
Numerous examples of progressive muscle diseases (also called myopathies) have been described in animals. Myopathies can be inherited, and many resemble various types of muscular dystrophy in humans. A Duchenne-like muscular dystrophy, similar to the one that affects dogs and humans, has been described in cats. It is a form of muscular dystrophy that attacks the leg and pelvic muscles and can lead to disease of the heart muscle. Signs can include progressive muscular weakness, difficulty swallowing, stiffness of gait, and the wasting away of muscle. Such myopathies can lead to heart muscle disease and death. Male cats are more likely to be affected.
Glycogen is a complex carbohydrate that is normally stored in the liver and muscles. The body converts it to glucose as a source of energy. Animals with glycogen storage diseases may weaken progressively until they are unable to rise from a lying position. To date, 5 of the 11 types of glycogen storage diseases characterized in humans have been identified in animals, including cats.
Cats with osteogenesis imperfecta inherit very fragile bones and loose joints. The long bones (such as the major bones of the front and hind legs) tend to be slender with thin outer layers. A veterinarian diagnosing the condition looks for evidence of recent breaks and fractures. The whites of the eyes of animals with osteogenesis imperfecta may also have a bluish tinge.
Several other congenital and inherited musculoskeletal disorders have been seen in cats. The most common is the presence of extra toes (called polydactyly). Cats can also be born without feet (apodia) or without certain bones in their limbs (hemimelia). Animals can also be born with split or missing toes, a condition called "lobster claw" defect or ectrodactyly syndrome. Finally, a few cats with toes that are fused together (syndactyly) have been reported.
Also see professional content regarding congenital and inherited anomalies of the musculoskeletal system in small animals.