Psoriatic arthritis is a type of arthritis belonging to the group known as the spondyloarthropathies. Psoriatic arthritis, as its name indicates, combines aspects of chronic joint pain and the skin disease psoriasis. Like rheumatoid arthritis, psoriatic arthritis is an inflammatory form of arthritis.

In 85 percent of patients who develop psoriatic arthritis, symptoms of psoriasis appear before symptoms of arthritis, or at the same time. In up to 15 percent of cases, arthritis precedes symptoms of psoriasis.

Symptoms of Psoriatic Arthritis

There are five types of psoriatic arthritis categorized by symptoms:

• Symmetric

• Asymmetric

• Distal interphalangeal predominant

• Spondylitis

• Arthritis mutilans

Symmetric psoriatic arthritis affects joints on both sides of the body. It is similar to rheumatoid arthritis because it affects multiple joints, but is generally considered milder than rheumatoid arthritis. With psoriatic arthritis there is usually less deformity than is characteristic of rheumatoid arthritis.

Asymmetric psoriatic arthritis can affect any joint of the body, but not the same joint on both sides of the body, as is the case with the symmetric type. Sausage-like toes and fingers from swelling are common characteristics of asymmetric psoriatic arthritis. Asymmetric is considered the most common type of psoriatic arthritis.

Distal interphalangeal predominant psoriatic arthritis primarily involves the distal joints of the fingers and toes. Nail changes are also a predominant feature.

Spondylitis psoriatic arthritis is characterized by inflammation of the spine. About half of the patients with the spondylitis type have a genetic marker, HLA-B27.

Arthritis mutilans is a very rare, but severe and disabling type of psoriatic arthritis. Joint deformity is the primary symptom, with small joints in the hands and feet most affected. Neck and lower-back pain are also problematic.

Diagnosis and Treatment of Psoriatic Arthritis

As with the other types of arthritis already mentioned, a medical history and physical examination are important during the diagnostic process. Blood tests are ordered, but with the intent of ruling out other types of arthritis. The erythrocyte sedimentation rate that is often elevated with rheumatoid arthritis may also be elevated with psoriatic arthritis. Elevated levels of blood uric acid are not uncommon, making it necessary to rule out gout.

The medications used to treat psoriatic arthritis are basically the same as those used to treat rheumatoid arthritis. Additionally, topical creams and light treatments help with the psoriasis.

Risk Factors and Prevalence of Psoriatic Arthritis

Men and women are affected equally by psoriatic arthritis. The disease usually has an age of onset between thirty and fifty years old. About 15 percent of psoriasis sufferers go on to develop psoriatic arthritis. Estimates suggest that 40 percent of people with psoriatic arthritis have a family history of psoriasis or arthritis, pointing to a genetic component. About 1 million Americans have psoriatic arthritis. About 2 percent of Caucasian people in North America suffer with psoriasis.