Information on the following diseases can be found in the Related Disorders section of this report:

• Rheumatoid Arthritis
• Reiter Syndrome

The course of psoriatic arthritis varies from case to case. Many affected individuals are only mildly affected. In approximately 20 percent of cases, affected individuals may develop a severe, disabling form of arthritis. Psoriatic arthritis may develop slowly with few symptoms or rapidly.

Psoriatic arthritis is sometimes broken down into five different variants. However, affected individuals may progress from one form of the disorder to another. In addition, one or more of the five variants may overlap in one individual. Consequently, determining the exact incidence rate of these variants is difficult. It is important to note that affected individuals will not have all of the symptoms listed below.

In most cases, psoriatic arthritis is characterized by inflammation of the joints as well as inflammation of the bones and tissues around the joints. Involvement of the joints often results in stiffness, especially in the morning (morning stiffness). Psoriasis of the nails or skin may precede or follow joint involvement. In many cases, symptoms of psoriasis occur first often preceding joint problems by several years.

Psoriasis is a skin condition characterized by distinctive silvery gray spots or plaques, with sharply defined margins. These scaly areas usually appear on the scalp, the elbows, the knees and the skin over the lower end of the spinal region. In some cases, affected individuals may develop small depressions (pitting) on the fingernails and toenails.

The last joints of the fingers or toes, lower back (sacrum), wrists, knees or ankles are usually most affected by psoriatic arthritis. Symptoms are usually not the same on both sides of the body (asymmetric). Rheumatoid nodules are often not present. Exacerbations and remissions tend to be more frequent, rapid, and complete than those occurring in rheumatoid arthritis, but progression to chronic arthritis and severe deformities may occur in some affected individuals. Aside from the skin involvement and joint pain, which may be disabling, people with psoriatic arthritis otherwise usually feel well.

Additional findings may include the development of a condition where the appearance of the toes resembles sausage (dactylitis), extensive destruction or dislocation of various large and small joints, and a severe deforming form of arthritis known as arthritis mutilans. Arthritis mutilans, which occurs in about five percent of affected individuals, is characterized by severe arthritis affecting the fingers and toes. Arthritis mutilans may progress to cause degenerative changes and loss of the calcium of bone (osteolysis).

In some cases, redness, swelling and pain affecting the eyes and inflammation of the transparent, thin membrane that protects and helps lubricate the eyelids and whites of the eyes (conjunctivitis) may also occur.
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The cause of psoriatic arthritis is not known. Several factors may contribute to the development of the disorder, including immunological, genetic, environmental, and/or other factors. Approximately 40 percent of affected individuals may have a family history of arthritis or psoriasis.

According to researchers, underlying genetic and immune mechanisms may be suggested by various findings, including an increased frequency of certain genetically determined "human leukocyte antigens" (HLAs) in some individuals with certain types of the disease. HLAs are proteins that play an important role in the body's immune system; they influence the outcome of transplantation and appear to affect an individual's predisposition to certain diseases. Specifically, the HLA-B27 antigen is present in the blood of many individuals with psoriatic arthritis. However, the implications of such findings are not fully understood.
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Depending upon the medical literature, of the many Americans who have psoriasis, anywhere from five to 40 percent develop psoriatic arthritis. It is more common in women and usually first appears between the ages of 20 and 50 years, but onset can occur at any age.
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Symptoms of the following disorders can be similar to those of psoriatic arthritis. Comparisons may be useful for a differential diagnosis:

Rheumatoid arthritis is a rheumatic disease characterized by chronic inflammation (arthritis) of one or more joints. Associated symptoms typically include swelling, abnormal warmth, tenderness or pain, and/or stiffness of affected joints that tends to be worse in the mornings. In severe cases, destructive changes may eventually result in limited mobility and possible deformity of affected joints. The skin is usually not involved in rheumatoid arthritis.

Acute gouty arthritis is an inflammation in and around a joint. This inflammation is caused by excess uric acid in the blood (hyperuricemia). Attacks occur suddenly and are accompanied by great pain; the big toe is a frequent site. This disorder is usually self-limiting and lasts, untreated, a couple of weeks.

Reiter's syndrome is a rare disorder characterized by arthritis, inflammation of the urinary tract (nongonococcal urethritis), and inflammation of the mucous membranes that line the eyes (conjunctivitis). Painful and swollen joints occur because of an underlying infection (reactive arthritis). Sores (lesions) may also occur on the skin and the mucous membranes of the mouth. In most cases, Reiter's Syndrome is transmitted through sexual contact (venereal). However, occasionally there is an underlying infection of the small bowel (enteric) that may contribute to the onset of Reiter's Syndrome. All the symptoms of the disease may not appear at once, and they may also disappear and then recur. (For more information on this disorder, choose “Reiter’s” as your search term in the Rare Disease Database.)
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Individuals with inflammation of multiple joints (polyarthritis) who test negative for rheumatoid arthritis should be examined for unrecognized or minimal psoriasis that may indicate the presence of this disorder.

Treatment of psoriatic arthritis is similar to that of rheumatoid arthritis, but with some significant differences. Use of antimalarial drugs is discouraged. Toxic reactions to gold salts appear more frequently in these individuals. Triamcinolone is a corticosteroid drug commonly used for treatment of this disorder. Oral steroids may have serious side effects, but injections of steroids into individual joints may be helpful for some individuals with psoriatic arthritis. For severely affected joints, folic acid antagonists and immunosuppressive drugs, especially methotrexate (caution: highly toxic) under careful medical supervision, have relieved psoriatic lesions and joint symptoms in some individuals. Physical therapy, tailored for the individual patient, may help to keep joints from stiffening.

One of the newer agents approved by the Food and Drug Administration (FDA) for the treatment of psoriatic arthritis is etanercept (Enbrel, Immunex Corporation, Seattle, WA). This drug is a biologic agent that blocks the actions of a naturally occurring protein involved in causing inflammation (tumor necrosis factor).
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Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government website.

For information about clinical trials being conducted at the National Institutes of Health (NIH) in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: prpl@cc.nih.gov

Psoriatic arthritis is sometimes treated with the folic acid antagonist and anti-cancer drug, methotrexate. The Arthritis Program at the National Institute of Arthritis, Musculoskeletal, and Skin Diseases studied this treatment to assess what effect long-term treatment with this drug has on patients with this disorder. Methotrexate (Rheumatrex) has been an FDA approved treatment for rhuematoid arthritis since 1993.

Results of a phase II clinical trial published in 2005 show the drug alefacept (Amevive) to be effective in treating psoriatic arthritis. Amevive is FDA-approved (2003) for treating severe plaque psoriasis. The drug works by disrupting the immune system, which spurs on the disease. This can result in the loss of T-cells and possibly increase the risk of getting cancer and serious infections. More information can be obtained on the Internet at:

www.amevive.com

Human antibodies called tumor necrosis factors ( infliximed, etanercept, adalimumab) are being investigated for the treatment of psortiatic arthritis. One study currently (2005) recruiting patients to examine this type of treatment is located in Lake Success , NY, and is sponsored by the Program in Novel Therapeutics with the NS-LIJ Health System. Information is available at:

Phone: (516) 562-1370
Email: furie@nshs.edu

A Rhode Island study specifically investigating etanercept (Enbrel) is currently (2005) recruiting patients. For information:

(401) 454-5959
Email: info@clinicalpartnersresearch.com

Researchers in a Phase III clinical trial in New York City at the NYU Hospital for Joint Disease are recruiting patients for a study of adalimumab as a treatment for psoriatic arthritis. Further information is available at:

Phone: (646) 356-9400

A study of saliva of psoriatic arthritis patients, sponsored by the University of Kentucky Chandler Medical Center, is currently (2005) being conducted. For more information, call:

Phone: (859) 323-5598 or (859) 323-5950.

To learn more about clinical trials investigating a wide-range of aspects for psoriatic arthritis, contact the Center for Rheumatology and Bone Research in Rockville, Maryland. Qualified participants will receive a free physical exam, tests, study medication and may possibly be compensated monetarily. For further information:

Phone: (301) 942-7833
Email: jfleming@arapc.com

The use of sulfasalazine is being tested for the treatment of seronegative spondyloarthropathies. The drug has been found to be helpful in the treatment of psoriatic arthritis, infectious arthritis, Reiter's syndrome, and ankylosing spondylitis with peripheral joint involvement. More studies are needed to determine the long-term safety and effectiveness of this treatment.

The use of the drug cyclosporin A is being studied for the treatment of individuals with severe psoriatic arthritis. Researchers are studying the long-term effectiveness and tolerability of the drug in affected individuals. More research is necessary to determine the long-term safety and effectiveness of low-doses of cyclosporin A in individuals with psoriatic arthritis.
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Bennett JC, Plum F., eds. Cecil Textbook of Medicine. 20th ed. Philadelphia, PA: W.B. Saunders Co; 1996:1471-2.

Fauci AS, et al., eds. Harrison's Principles of Internal Medicine, 14th Ed. New York, NY: McGraw-Hill, Inc; 1998:1949-51.

Kelley WN, et al., eds. Textbook of Rheumatology. 4th ed. Philadelphia, PA: W.B. Saunders Company; 1993:974-82.

Champion RH, et al., eds. Textbook of Dermatology. 5th ed. Cambridge, MA: Blackwell Scientific Publications; 1992:1440-6.

JOURNAL ARTICLES
Gladman DD, Current concepts in psoriatic arthritis. Curr Opin Rheumatol. 2002;14:361-6.

Barton AC, Genetic Epidemiology: psoriatic arthritis. Arthritis Res. 2002;4:247-51.

Sarzi-Puttini P, et al., Long-term safety and efficacy of low-dose cyclosporin A in severe psoriatic arthritis. Rheumatol Int. 2002;21:234-8.

Mease PJ, Etanercept: a new era in the treatment of psoriatic arthritis. Am J Manag Care. 2002;8:S181-93.

Ruderman EM, Current perspectives in the recognition and management of psoriatic arthritis: implications for integrated patient care. Am J Manag Care. 2002;8:S171-80.

Krueger GG, Clinical features of psoriatic arthritis. Am J Manag Care. 2002;8:S160-70.

Clegg DO, et al., Comparision of sulfasalazine and placebo in the treatment of psoriatic arthritis. Arthritis Rheum. 1996;39:2013-20.