Psoriasis affects at least 7.5 million Americans. It’s the most common autoimmune disease in the United States. About 30 percent of American’s with psoriasis will develop psoriatic arthritis.

Psoriatic arthritis mutilans is a rare form of psoriatic arthritis. It causes bone tissue to disappear. It develops in about 5 percent of people with psoriatic arthritis. This form of arthritis is sometimes called “opera glass hand” or “telescopic finger.” Psoriatic arthritis mutilans usually happens in the hands. It sometimes affects the wrists, feet, or spine.

Keep reading to learn what symptoms to look out for, what causes this condition, and more.

Everyone that develops psoriatic arthritis will experience arthritis symptoms. This includes stiff joints and decreased range of motion.

If you develop psoriatic arthritis mutilans, the bone in the affected joints will begin to disappear. This makes it impossible to straighten or bend the affect joint.

Over time, the affected joints shorten. This causes loose skin to develop in the affected areas. The loose skin retracts and causes nearby organs to take on a distinctive appearance.

There are five kinds of psoriatic arthritis. Psoriatic arthritis mutilans is considered the most severe. To understand how psoriatic arthritis mutilans develops, it’s helpful to understand how psoriatic arthritis occurs.

You usually develop psoriatic arthritis if you’ve already had psoriasis. Psoriasis is caused by an autoimmune response in your body. Your immune system attacks your healthy cells. This causes inflammation throughout the body, including the joints. It’s the main cause of arthritis.

Long-term inflammation of your joints can cause permanent damage. Certain bones, like those connected to frequently used joints, will start to erode. When this happens, it’s known as psoriatic arthritis mutilans.

Psoriatic arthritis mutilans is rare. There’s little evidence on how to predict it will develop. What we do know is people who don’t have psoriatic arthritis won’t get psoriatic arthritis mutilans.

So far, research into the risk factors for psoriatic arthritis is inconclusive. Childhood obesity and diagnosis of psoriasis at a young age could be risk factors. But the only strong indicator of developing psoriatic arthritis is family history of the condition.

Learn more: Psoriatic arthritis »

In some cases, people diagnosed with psoriatic arthritis didn’t know they had psoriasis. In 85 percent of psoriatic arthritis cases, symptoms of psoriasis are obvious before arthritis is apparent.

To diagnose psoriatic arthritis mutilans, your doctor will first confirm you have arthritis. After checking your joints for signs of swelling or tenderness, you’ll receive diagnostic testing.

Your doctor may order lab tests to check for inflammation or the presence of certain antibodies. Both can point to arthritis. You doctor will also likely recommend an X-ray or other imaging test to assess joint damage.

Once your doctor diagnosis you, they’ll test a blood sample to find out what kind of arthritis you have. For example, if the rheumatoid factor (RF) and cyclic citrullinated peptide (CCP) antibodies are in your blood, you have rheumatoid arthritis (RA).

At this time, there isn’t a lab biomarker for psoriatic arthritis or the psoriatic arthritis mutilans subset. Psoriatic arthritis mutilans is diagnosed by checking the severity of the bone destruction. There are very few conditions associated with such a severe level of bone loss.

Psoriatic arthritis mutilans is a progressive disease. The sooner it’s diagnosed, the more likely you can slow its progression. The treatment goals are to manage your symptoms and help maintain or improve your quality of life.

Most treatments include the disease modifying anti-rheumatic agent (DMARD) methotrexate (Trexall), an anti-TNF inhibitor, or both.

Methotrexate may ease your arthritis symptoms. But it’s unclear if it can slow bone loss.

Some research shows drugs called anti-TNF inhibitors can stop symptoms of psoriatic arthritis from getting worse. Anti-TNF inhibitors change your body’s anti-inflammatory responses. Suppressing inflammation keeps joints from feeling stiff or painful.

The inhibitors may also help restore joint function. In one 2011 study, researchers found the drug etanercept (Enbrel) restored some function.

This type of arthritis can cause permanent disability if it’s not treated. But a diagnosis of psoriatic arthritis mutilans means something different today than in the days when it was called “opera glass hand.” Your outlook improves dramatically when you detect and treat psoriatic arthritis. Early treatment can prevent bone loss.

Bone tissue can’t be restored. But treating your psoriatic arthritis will slow the destruction of your bones. Instead of losing the use of your fingers or toes, you will most likely be able to keep them functioning.

Learn more: Psoriatic arthritis: Prognosis, life expectancy, and quality of life »

Diseases that are difficult to predict are difficult to prevent. There are some things you can do to lessen your risk for developing psoriasis and psoriatic arthritis.

Maintaining a healthy weight and consistent exercise routine can help prevent infections and disease. These are believed to be psoriasis triggers.

Not smoking can also make your body more responsive to treatment. If your other arthritis symptoms improve because of treatment, the “mutilans” effect will slow down.

Remember that psoriasis is believed to be mostly genetic. Look into your family history to find out if there is psoriasis. This information can help you know if you’re at a higher risk.

If you find out you have a family history of psoriasis, tell your doctor. And also be on the lookout for symptoms. Early detection and treatment will make dealing with psoriasis a lot easier.

Learn more: Psoriasis »