Bone Deformity and Dwarfism in Cats

Feline dwarfism was first seen in the early 1930’s but became obscure shortly after World War II. However, cats suffering from this condition were seen again in the early 1980’s and were soon recognized as their own breed called "Munchkin". 

There are a variety of bone disorders that can cause deformities in your cat. Most of these conditions are inherited and present at birth. Dwarfism is an example of a bone deformity. This is typically seen in 1 in 15,000 feline births.

The symptoms associated with bone deformities in cats depend on the cause of the condition. They can range from mild to severe. Some of the most commonly seen symptoms in cats with these types of conditions include:

• Hip dysplasia
• Kneecap displacement
• Lameness
• Loss of appetite
• Pain in affected joints
• Swelling of joints
• Tumor growth
• Disc degeneration
• Small stature in cases of dwarfism

Types

There are many types of bone deformities that can occur in domestic cats. They can be present when the cat is born or they can develop over time. Below are some types of bone deformities found in cats.

• Immune-mediated arthritis
• Arthritis caused by a cancerous growth such as a sarcoma
• Hip dislocation
• Knee dislocation
• Joint disorders caused by nutritional deficiencies 
• Inflammation of the bone
• Developmental bone conditions
• Bone fractures that heal improperly
• Bone deformities caused by infection in the joint
• Dwarfism, also known as Munchkin syndrome

Many bone disorders and deformities in cats are genetic or inherited. This means that the gene for it exists somewhere in the cat’s bloodline. Others occur after birth, due to extenuating circumstances. Below are some of the most likely causes of bone disorders in domestic felines. 

• Degenerative Joint Disease
• Osteoarthritis
• Septic arthritis
• Traumatic joint injury
• Mutation of the gene that causes dwarfism
• Osteomyelitis, also known as inflammation of the bone
• Scottish Fold Osteodystrophy, a genetic condition that causes spinal deformities
• Osteochondromatosis, a condition that causes multiple abnormal bone growths

In order for your veterinarian to make an accurate diagnosis he must perform a complete examination. First, he will take a detailed history and obtain any pertinent information that may help discover the cause of the abnormality. After taking a medical history, your doctor will perform a thorough examination. He will look for malformed joints, watch your cat walk and evaluate his overall demeanor.

Your veterinarian may draw blood in order to run some laboratory tests. These may include a CBC to check for infection in the bone and a urinalysis. If a bony abnormality is present, your doctor may also take X-rays to determine the cause. X-rays can reveal bone fractures and give the doctor information as to the age of the injury. More detailed diagnosis imaging tests such as an MRI or CT scan may also be done if a diagnosis is elusive or needs to be confirmed.

Dwarfism is typically diagnosed upon visual inspection and examination of your cat. Some doctors have done genetic testing to determine the cause, but these tests are expensive. 

The treatment for bone deformities in felines depends on the diagnosis. Certain types of fractures may be treated with the placement of an external splint. Fractures that have healed improperly may be corrected with surgery. During these surgeries doctors often place pins, screws and plates to repair joints. If a malignant tumor is the cause of the problem, doctors may opt to amputate the affected limb in an effort to stop the spread of cancer. In cats with arthritis, doctors may prescribe anti-inflammatory medications to reduce swelling and pain. Doctors may also place the cat on a weight reduction program if that is aggravating the condition. Reducing body weight takes strain off of the joints and can help reduce pain significantly.

Cats that are treated for fractures often recover within just a few weeks. In those that have surgery to correct a broken bone, the average recovery time is 6 weeks. During this time, doctors may perform treatment such as laser therapy, which aids in healing. Studies have shown animals treated with laser therapy recover faster than those who do not receive it. This treatment uses infrared heat to penetrate the tissues and promote rapid healing. It is painless and only takes minutes to perform.

If your cat has an abnormality and discomfort from arthritis, the recovery time varies depending on how well the anti-inflammatory medications are tolerated. Most cats begin to feel better two weeks after starting medication. 

Cats diagnosed with dwarfism will not experience any changes as they age in regards to recovery. Veterinarians are still working to discover if cats with this disorder suffer any long term effects or shortened lifespan. To date, this has not been determined but studies are ongoing around the world.