Living with Psoriatic Arthritis (PsA): An Overview Of PsA
This article was originally written by: Scott P. Edwards. Scott Edwards is a freelance health and medical writer based in Holliston, Mass. He has written for Harvard Medical School, Dana-Farber Cancer Institute, the Salk Institute for Biological Studies, and Nature Publishing Group. This article was reviewed by SAA's Medical And Scientific Advisory Board for content and accuracy.
This article was published in SAA's news magazine, Spondylitis Plus.
When you hear about a skin disease like psoriasis, you probably don’t link it to such things as joint pain and stiffness. But nearly 5 percent of Americans with psoriasis have a related condition, called psoriatic arthritis (PsA), which can lead to permanent and debilitating joint damage.
PsA is a type of arthritis that often occurs after psoriasis; a common, chronic skin condition that causes raised red patches on the skin, often with a silvery scale (psoriatic skin lesions). The arthritis may be mild and involve only a few joints, especially at the ends of fingers or toes, or it may be severe and affect many joints, including the spine. An estimated 600,000 Americans—and more than 12 million people worldwide—have PsA, which may strike at any age, but typically occurs between the ages of 30 and 50.
In PsA, immune cells are activated and produce too much of a protein called tumor necrosis factor-alpha, or TNF-alpha. This protein causes inflammation in the skin, which can cause skin cells to grow too quickly. As skins cells build up, raised, red patches form. The protein also causes inflammation of the joints, which can lead to pain and progressive joint damage.
PsA and ankylosing spondylitis (AS) are considered genetically and clinically related because both are inflammatory diseases related to the HLA-B27 gene. HLA-B27 is a powerful predisposing gene associated with several rheumatic diseases. The gene itself does not cause disease, but can make people more susceptible. While a number of genes are linked to PsA, the highest predictive value is noted with HLA-B27.
There are five distinct types of PsA:
- Symmetric PsA, which affects the same joints in multiple matching pairs on both sides of the body, can be disabling, causing varying degrees of progressive joint destruction and loss of function.
- Oligoarticular (asymmetric) PsA, which affects only a few joints but not matching pairs on opposite sides of the body, is often a milder form of the disease.
- Distal interphalangeal predominant PsA, which primarily affects the joints closest to the toenails and fingernails, is sometimes confused with osteoarthritis.
- Psoriatic spondylitis, which affects the spinal column from the neck to the lower back.
- Arthritis mutilans, a rare but severe, destructive form of the disease that leads to loss of joint function.
About 20 percent of patients with PsA will develop spinal involvement. Inflammation of the
spine can lead to complete fusion, as in AS, or affect only certain areas such as the lower back or neck. Patients who are HLA-B27-positive are more likely than others to have their disease progress to the spine.
While PsA is a single disease, it can have many different symptoms that affect the skin and joints, including:
- Swelling of an entire finger or toe, which can cause them to look like sausages
- General joint pain and stiffness, especially in the morning
- Joint swelling
- Back pain and stiffness, primarily in the lower back, neck and upper back
- Reduced range of motion
- Painful, often throbbing, joints
- Psoriatic skin lesions
- Nail changes, including pitting of the fingernails and toenails, which occurs in almost all patients
Other symptoms include generalized fatigue and redness or pain in the eye. Thirty percent of
PsA patients have eye inflammation (conjunctivitis) and seven percent have iritis, or inflammation of the colored part of the eye.
The symptoms of PsA, which vary from person to person, can change in severity. Skin symptoms typically appear before the joints become involved, sometimes up to 10 years before. Without treatment, many of these symptoms can lead to progressive, permanent joint damage.
Diagnosing psoriatic arthritis can be tricky, primarily because it shares similar symptoms with other diseases such as osteoarthritis, rheumatoid arthritis and gout. Because of this, misdiagnosis can often be a problem. Early diagnosis, however, is important because long-term joint damage can be warded off better in the first few months after symptoms arise.
Primary care physicians and dermatologists can diagnose PsA, but a rheumatologist, who specializes in arthritis, may be able to better spot the telltale signs of the disease.
There are no definitive tests for diagnosing PsA. Doctors diagnose the disease primarily based on a patient’s clinical presentation and process of elimination (for example, the presence of rheumatoid factor in the blood can differentiate rheumatoid arthritis from PsA). A complete medical history and physical examination, as well as blood tests, X-rays and MRI scans of joints that have symptoms, can be used to diagnose PsA.
In the early stages of the disease, standard X-rays usually don’t reveal signs of PsA and may not aid in diagnosis. In later stages, however, they may show characteristic changes that distinguish PsA from other rheumatic diseases. One of these is the “pencil-in-cup” phenomenon, in which the end of a bone gets whittled down to a sharp point where it enters a joint. Changes in the peripheral joints and spine, which also occur in later stages of disease, can also support a PsA diagnosis.
Treatment of PsA has changed dramatically over the past few decades. Thirty years ago, patients with PsA and rheumatoid arthritis were frequently treated with weekly gold injections. Twenty years later the use of anti-TNF drugs revolutionized the treatment of the disease and scientists continue to learn more about the disease and how to successfully treat it.
The most common treatments for PsA are often used to treat AS, and include:
- NSAIDs – nonsteroidal anti-inflammatory drugs, which are sold either over the counter or in prescription strength, help reduce pain, inflammation and stiffness and have proven effective for many patients with PsA. These drugs include ibuprofen (Advil, Motrin), indomethacin (Indocin) and naproxen (Aleve) among others.
- DMARDs – disease-modifying antirheumatic drugs, which help to limit the amount of joint damage caused by the disease. Methotrexate (Trexall) is the most commonly used DMARD.
- Sulfasalazine (Azulfidine) has a moderate effect in treating PsA.
- Immunosuppressants – drugs that suppress the immune system, which normally protects the body, but attacks healthy tissue in autoimmune diseases like PsA. Azathioprine (Imuran), cyclosporine (Sandimmune) and leflunomide (Arava) are commonly prescribed. Because of serious side effects, these drugs are only used in patients with severe PsA.
- TNF-alpha inhibitors – drugs that block the action of the proinflammatory protein involved in PsA. These include adalimumab (Humira), etanercept (Enbrel), golimumab (Simponi) and infliximab (Remicade).
An experimental drug, called apremilast, has proven to be moderately effective in treating late-stage PsA compared to other leading therapies. This drug inhibits the enzyme phosphodiesterase 4 and tamps down inflammation.
Exercise is essential for preserving strength and maintaining range of motion. Isometric exercises, which contract muscles without joint motion, may be less damaging to inflamed joints. Physical therapy may also help patients maximize the function of arthritic joints.
Patients should consult with their physician to determine which of these treatments is most appropriate for their condition.
While PsA can certainly affect an individual’s quality of life, the symptoms of the disease can be managed effectively. Paying attention to symptoms of the disease and addressing them as soon as they arise can, in fact, lead to positive outcomes.