Psoriasis - Causes

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Psoriatic Arthritis

Psoriatic arthritis (PsA) is an inflammatory condition that leads to stiff, tender, and inflamed joints. Estimates on its prevalence among people with psoriasis range from 2 - 42%. Psoriasis patients who also have AIDS and people with severe psoriasis are at higher risk for developing PsA.

About 80% of PsA patients have psoriasis in the nails. Arthritic and skin flare-ups tend to occur at the same time. It is not clear whether psoriatic arthritis is a unique disease or a variation of psoriasis, although evidence suggests they are both caused by the same immune system problem.

PsA is often divided into five forms. The forms differ according to the location and severity of the affected joint:

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• Symmetric PsA: Symptoms occur in the same location on both sides of the body. The condition usually affects multiple joints. In about half of the cases, symmetric PsA will get worse. The condition is very similar to, but less disabling than, rheumatoid arthritis. The psoriasis itself is often severe.
• Asymmetric PsA: This form involves periodic joint pain and redness, usually in only one to three joints, which can be the knee, hip, ankle, wrist, or one or more fingers. The pain does not occur in the same location on both sides of the body.
• Distal interphalangeal predominant (DIP): DIP involves the joints of the fingers and toes closest to the nail. It occurs in about 5% of PsA cases.
• PsA in the spine: Inflammation in the spinal column (spondylitis) is the primary symptom in about 5% of PsA cases. Such patients may have stiffness and burning sensations in the neck, lower back, sacroiliac, or spinal vertebrae. The spine can be involved in many patients with PsA, even though stiffness and burning sensations in these areas are not the primary symptoms. When it affects the spine, psoriatic arthritis most frequently targets the sacrum (the lowest part of the spine). Movement is difficult.
• Arthritis mutilans: This is a severe, deforming, and progressive form of arthritis. It affects less than 5% of PsA cases. It mainly affects the small joints of the hands and feet, but it can also be found in the neck and lower back. Arthritic and skin flares and remissions tend to coincide.

People who start to smoke after developing psoriasis may delay the onset of psoriatic arthritis. However, research has also linked smoking to an increased risk of psoriasis, and because smoking causes serious health problems, it should not be considered as a way to delay this type of psoriasis.

Review Date: 10/21/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).