PSORIATIC ARTHRITIS OVERVIEW

Psoriatic arthritis is a type of arthritis that causes joint pain, swelling, and stiffness in people with psoriasis. Psoriasis is a chronic skin condition that causes patches of thick, inflamed red skin that are often covered with silvery scales.

Psoriatic arthritis affects men and women equally. Most people who develop psoriatic arthritis have skin symptoms of psoriasis first, followed by arthritis symptoms. However, in about 15 percent of cases, symptoms of arthritis are noticed before psoriasis appears. In another 15 percent of cases, psoriatic arthritis is diagnosed at the same time as psoriasis.

PSORIATIC ARTHRITIS RISK FACTORS

Researchers have not identified the exact cause of psoriatic arthritis. However, they believe that the disease develops due to a combination of genetic, immunologic, and environmental factors.

Genetic factors — About 40 percent of people with psoriasis or psoriatic arthritis have family members with psoriasis or psoriatic arthritis. This means that a close relative of a patient with psoriatic arthritis is about 50 times more likely to develop the disease than an unrelated person. If an identical twin has psoriatic arthritis, the other twin is very likely to have or to develop the condition.

Genetic researchers have identified areas on certain chromosomes that may increase the risk of developing psoriatic arthritis. Other genetic factors may contribute to the severity of disease.

Immunologic factors — A variety of immune system abnormalities have been noted in people with psoriatic arthritis.

Environmental factors — Exposure to certain infections, including those caused by bacteria and viruses, may also contribute to the development of psoriatic arthritis. Some experts believe there is a link between streptococcal infection and the development of psoriasis and psoriatic arthritis, although the link has not been proven. Psoriatic arthritis also occurs more commonly in people infected with the human immunodeficiency virus (HIV) than in the general population.

Psoriasis frequently appears at sites where there is skin trauma. This is called the Koebner phenomenon. Some patients develop arthritis in an injured joint.

PSORIATIC ARTHRITIS SYMPTOMS

Symptoms of psoriatic arthritis include:

• Pain and tenderness in the joints (picture 1)
• Difficulty moving or stiffness in the joints and/or in the back. About half of all patients have morning stiffness lasting more than 30 minutes.
• Skin patches (also called plaques) that are dry or red, usually covered with silvery-white scales, which may have raised edges (picture 2)
• Nail abnormalities, such as pitted, discolored, or crumbly nails (picture 3)

Some people with psoriatic arthritis have more difficulty with stiffness and immobility than with joint pain. (See "Clinical manifestations and diagnosis of psoriatic arthritis".)

Patterns of psoriatic arthritis — Psoriatic arthritis tends to affect certain groups of joints. The following terms are used to describe patterns of psoriatic arthritis:

• Distal arthritis — This type of psoriatic arthritis affects the end joints of the fingers and toes.
• Asymmetric oligoarthritis — This type of psoriatic arthritis affects fewer than five small or large joints in the body but does not necessarily occur on both sides of the body (for example, a person might experience joint pain in one elbow but not the other).
• Symmetric polyarthritis — This type of psoriatic arthritis affects five or more joints on both sides of the body (ie, the right and left knee). It produces symptoms similar to those of rheumatoid arthritis.
• Arthritis mutilans — This type of psoriatic arthritis deforms and destroys the joints, and it is often accompanied by a shortening of the affected fingers or toes.
• Spondyloarthropathy — This arthritis affects the joints of the spine.

Polyarthritis is the most common type of psoriatic arthritis, followed by oligoarthritis. Less than 20 percent of patients experience distal arthritis, but those who do may also have spondyloarthritis. Arthritis mutilans, the deforming type of arthritis, can occur along with any other pattern of arthritis.

Associated problems — In addition to the joint pain and stiffness that psoriatic arthritis causes, there may also be swelling in the areas where tendons attach to bones, a condition called enthesitis. Sites that are commonly involved include the Achilles tendon attachment to the back of the heel, the attachment of plantar fascia (the tendon in the sole of the foot) to the heel, and the area that tendons attach to the pelvic bones. Another condition, tenosynovitis, can occur when the sheaths surrounding certain tendons, especially those in the hands and arms, become swollen and inflamed.

Almost half of people with psoriatic arthritis also experience dactylitis, which causes an entire finger or toe to swell (sometimes called sausage finger or toe). Dactylitis may be associated with progressive joint damage (picture 4). People with psoriatic arthritis sometimes develop swelling of the hands and feet that is not limited to the joints. This swelling may occur before any joint symptoms of psoriatic arthritis are noted.

Eighty to 90 percent of people with psoriatic arthritis have nail problems. They may develop pitted nails, which look as if someone has taken a pin and pricked the nail several times, or there may be early separation of the nail from the nail bed. The severity of a person's nail problems is often similar to the severity of the skin and joint problems (picture 3).

In some cases, people with psoriatic arthritis also experience eye problems. Inflammation of the structures of the eye can cause eye pain and redness and is referred to as uveitis or iritis.

PSORIATIC ARTHRITIS DIAGNOSIS

Healthcare providers diagnose psoriatic arthritis by obtaining the medical history, performing a physical examination, and taking x-rays of the joints to check for inflammation. Blood tests or joint fluid tests may be done to rule out other diseases, such as rheumatoid arthritis and gout.

In some cases, a magnetic resonance imaging test (MRI) may be used to detect joint and soft-tissue inflammation that cannot be seen on x-rays. Because psoriatic arthritis may be associated with a loss in bone mineral density, tests may also be used to determine if you are at risk for osteoporosis or have an increased risk of bone fractures. (See "Patient information: Bone density testing (Beyond the Basics)".)

Psoriatic arthritis may be confused with other forms of arthritis, such as rheumatoid arthritis. However, the skin lesions, nail problems, and specific patterns of inflammation mean that it is usually possible to definitively distinguish psoriatic arthritis from other forms of inflammatory arthritis.

PSORIASIS TREATMENT

Psoriatic skin disease may be treated with topical applications (creams or lotions) or phototherapy. Skin problems that are resistant to topical therapy may require the use of oral treatments (pills). (See "Patient information: Psoriasis (Beyond the Basics)".)

Although effective in controlling the skin symptoms in most patients, none of these treatments work in all patients. Moreover, none can cure psoriasis; most patients have a flare of symptoms if treatment is discontinued. Thus, prolonged therapy is generally required.

PSORIATIC ARTHRITIS TREATMENT

Psoriatic arthritis treatment can help to relieve joint pain and stiffness as well as the other symptoms of psoriasis. More detailed information is available separately. (See "Treatment of psoriatic arthritis".)

Exercise and physical therapy — Treatments such as heat, exercise, and physical therapy may also help to relieve the pain and stiffness associated with psoriatic arthritis. A separate article discusses exercise and arthritis. (See "Patient information: Arthritis and exercise (Beyond the Basics)".)

Nonsteroidal antiinflammatory drugs (NSAIDs) — NSAIDs can help to control inflammation and to relieve the pain of psoriatic arthritis. NSAIDs must be taken continuously and at a sufficient dose to have an antiinflammatory effect.

NSAIDs must usually be taken for several weeks before their full degree of effectiveness as an antiinflammatory is known. If the initial dose of an NSAID does not improve symptoms, a clinician may recommend increasing the dose gradually or switching to another NSAID.

• Nonselective NSAIDs include over-the-counter drugs, such as aspirin, ibuprofen, and naproxen, and a number of prescription-strength NSAIDs.
• Selective NSAIDs (also called COX-2 inhibitors) are as effective as nonselective NSAIDs and are less likely to cause gastrointestinal injury and side effects. Celecoxib (Celebrex®) is the only COX-2 inhibitor currently available in the United States.

Detailed information about NSAIDs is available in a separate article. (See "Patient information: Nonsteroidal antiinflammatory drugs (NSAIDs) (Beyond the Basics)".)

Glucocorticoid injections — Glucocorticoids, also called steroids, can suppress inflammation and can relieve pain when injected into affected joints. Oral glucocorticoids are not usually recommended for people with psoriatic arthritis because they may cause a severe form of skin psoriasis.

Joint injections have few side effects, but some people experience a brief flare of pain after an injection. There is also a very small risk of joint infection.

Methotrexate — Methotrexate is a disease-modifying antirheumatic drug (DMARD) that reduces excessive production of skin cells and that may also suppress the immune system. It is often recommended for people with multiple swollen joints caused by psoriatic arthritis.

It is usually taken once per week as a pill or by injection. Treatment with higher doses may require that it be injected under the skin, which may be done by a patient or family member.

Taking folic acid or folinic acid can reduce the risk of certain methotrexate side effects, including risk of liver problems related to methotrexate. Patients who use methotrexate should not drink alcohol. The most serious potential side effects of methotrexate include liver toxicity, lung disease, and bone marrow suppression. (See "Patient information: Disease-modifying antirheumatic drugs (DMARDs) (Beyond the Basics)".)

Sulfasalazine — Sulfasalazine (sulphasalazine, salazopyrin) is a disease modifying antirheumatic drug (DMARD) that may be effective for the joint pain and skin lesions associated with psoriatic arthritis.

However, not all patients benefit from sulfasalazine, and many patients cannot tolerate it due to gastrointestinal side effects. Patients who are allergic to sulfa drugs should not use sulfasalazine. (See "Patient information: Sulfasalazine and the 5-aminosalicylates (Beyond the Basics)".)

Leflunomide — Leflunomide is a disease-modifying antirheumatic drug (DMARD) that can improve both skin and joint disease symptoms. (See "Patient information: Disease-modifying antirheumatic drugs (DMARDs) (Beyond the Basics)".)

Possible side effects include diarrhea and elevated liver enzymes, and only about 40 percent of people with psoriatic arthritis benefit from this treatment. Experts may recommend leflunomide if you have not adequately responded to or have had side effects with methotrexate.

TNF inhibitors — Tumor necrosis factor (TNF)-alpha inhibitors are among the group of drugs called biologic DMARDs or biologic response modifiers. These drugs interfere with inflammation and the immune response. Drugs in this class include proteins that interfere with the actions of TNF, such as etanercept (Enbrel®), adalimumab (Humira®), infliximab (Remicade®), and golimumab (Simponi). If a traditional DMARD, such as methotrexate, has been ineffective, a medication from this class of agents will often be effective. (See "Overview of biologic agents in the rheumatic diseases".)

Biologic agents, such as the TNF inhibitors, usually work rapidly, often within two weeks. They may be used alone or in combination with other DMARDs, NSAIDs, and/or glucocorticoid injections. Because of their very high cost, they are often reserved for people who have not responded fully to DMARDs or who cannot tolerate DMARDs in doses large enough to control psoriatic arthritis symptoms.

All biologic agents must be either injected or given intravenously, depending on the medication. Humira® and Enbrel® are injected under the skin by the patient, a family member, or a nurse. Intravenous infusion is necessary for Remicade®; this is typically done in a doctor's office or an outpatient infusion center and takes one to three hours to complete.

Cyclosporine — Cyclosporine is a drug that suppresses the immune system and is also used to treat severe psoriasis and psoriatic arthritis. It was used more in the past, before the availability of the TNF inhibitors, but still may be helpful for some people with psoriatic arthritis. It may take three to four months before a response is seen. Adding cyclosporine to methotrexate may be more effective than either treatment alone. Side effects of cyclosporine can include impaired kidney function and high blood pressure.

SUMMARY

• Psoriatic arthritis is a type of arthritis that affects some people with psoriasis, a disorder that causes inflammation and thickening of the skin.
• Researchers have not identified the exact cause of psoriatic arthritis. However, they believe that the disease develops due to a combination of genetic, immune, and environmental factors. (See 'Psoriatic arthritis risk factors' above.)
• Psoriatic arthritis can cause joint pain, immobility, and stiffness; dry, red patches (plaques) also form on the skin. Some people also experience problems with their fingernails or eyes. (See 'Psoriatic arthritis symptoms' above and 'Associated problems' above.)
• Psoriatic arthritis tends to affect certain groups of joints. The most common type of psoriatic arthritis affects five or more joints on both sides of the body. (See 'Patterns of psoriatic arthritis' above.)
• Physical examination, x-rays, and, sometimes, magnetic resonance imaging (MRI) are used to diagnose psoriatic arthritis. Skin and nail symptoms, as well as the pattern of joint pain and stiffness, help to determine if arthritis is psoriatic or not. (See 'Psoriatic arthritis diagnosis' above.)
• Symptoms of skin psoriasis are usually treated with creams or lotions and, in some cases, with light therapy. (See 'Psoriasis treatment' above.)
• Heat and physical therapy may help to relieve joint pain and stiffness. Joint inflammation is often treated with medications given as pills or injections. (See 'Psoriatic arthritis treatment' above.)

WHERE TO GET MORE INFORMATION

Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient information: Psoriasis (The Basics)
Patient information: Psoriatic arthritis in adults (The Basics)
Patient information: Disease modifying antirheumatic drugs (DMARDs) (The Basics)
Patient information: Psoriatic arthritis in children (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient information: Bone density testing (Beyond the Basics)
Patient information: Psoriasis (Beyond the Basics)
Patient information: Arthritis and exercise (Beyond the Basics)
Patient information: Nonsteroidal antiinflammatory drugs (NSAIDs) (Beyond the Basics)
Patient information: Joint infection (Beyond the Basics)
Patient information: Disease-modifying antirheumatic drugs (DMARDs) (Beyond the Basics)
Patient information: Sulfasalazine and the 5-aminosalicylates (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Clinical manifestations and diagnosis of psoriatic arthritis
Pathogenesis of psoriatic arthritis
Treatment of psoriatic arthritis
Overview of biologic agents in the rheumatic diseases

The following organizations also provide reliable health information.

• The Arthritis Society of Canada
  (www.arthritis.ca)
• Arthritis Foundation
  (www.arthritis.org)
• National Library of Medicine
  (www.nlm.nih.gov/medlineplus/ency/article/000413.htm, available in Spanish)
• National Psoriasis Foundation
  (www.psoriasis.org)

Patient support — There are a number of online forums where patients can find information and support from other people with similar conditions.

• About.com Arthritis Forum
  (http://arthritis.about.com/forum)

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