Overview of Psoriatic Arthritis
Medically reviewed by Dr. C.H. Weaver M.D. Medial Editor 8/2020
Psoriatic arthritis is a condition that stems from psoriasis, an autoimmune disease in which the body’s immune system attacks the skin, resulting in scaly, red patches on the skin. In some psoriasis patients, the immune system attacks the joints as well, leading to inflammation and the condition known as psoriatic arthritis. Overall about 1 to 3 % of the population of the United States has psoriasis and approximately 30% of people with psoriasis have psoriatic arthritis.
Psoriatic arthritis typically affects people between the ages of 30 and 50 and individuals and although the majority of affected individuals will have psoriasis of the skin, although some will develop joint disease prior to skin manifestations. Symptoms of psoriatic arthritis are highly variable among patients, coming and going over time and affecting one or many joints of the body. Psoriatic arthritis can be painful and could affect any joint in the body, especially larger ones in the lower extremities, the joints of fingers and toes, and the spine. But it can also cause swelling in areas where tendons and ligaments attach to bones, known as enthesitis, or swelling of an entire finger or toe, known as dactylitis.
In recent years a variety of biologic medications have become available that have improved the treatment of psoriatic arthritis.
Symptoms & Signs of Psoriatic Arthritis
Individuals with psoriatic arthritis will typically have documented psoriasis consisting of characteristic thick, red skin with silvery patches and nail changes.
Joint Signs & Symptoms
- Joint pain and reduced physical mobility
- Pain and swelling commonly felt in hands, feet, and even hip joints.
- Sausage-like fingers or toes (dactylitis)
- Swelling along the entire length of finger(s) and toe(s).
- Tenderness (enthesitis)
- Tenderness or pain where tendons and ligaments attach to bones.
General Signs & Symptoms
- Periods of extreme tiredness.
Back pain can be a symptom of psoriatic spondylitis which usually occurs in men who have onset of psoriasis late in life. Back pain may involve one, or both sacroiliac joints. Back pain is worse in the morning, getting out of bed, and is associated with spine stiffness. Spondylitis may affect the low back, chest, and/or the neck. In the cervical spine, limitation of motion is a primary manifestation of neck involvement. The activity of skin and nail disease does not necessarily correlate with joint or spine involvement.
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Diagnosing Psoriatic Arthritis
The diagnosis of psoriatic arthritis is mainly based upon a spectrum of characteristic findings noted in the history, physical examination, and radiographic findings. Psoriasis is typically present prior to, or at the onset of joint disease. Only a minority of individuals will have characteristic joint disease before psoriasis.
Psoriatic arthritis may be misdiagnosed as rheumatoid arthritis, osteoarthritis, or gout. Rheumatoid arthritis generally involves joints that are symmetrical on both sides of the body; however, some forms of psoriatic arthritis look very similar. One way to potentially differentiate between the two is having characteristic psoriatic skin or nail changes. Usually, patients with early signs of psoriatic arthritis will have had psoriasis for several years when they begin to feel discomfort in the joints.
There are no tests that are specific for the diagnosis of psoriatic arthritis. Laboratory findings of HLA-B27 positivity, and blood test signs of inflammation (elevated C reactive protein or erythrocyte sedimentation rate) are compatible but not specific for psoriatic arthritis.
Plain x-ray films of the lower spine will show definite signs of arthritis in the sacroiliac joints when affected.
Silman AJ, Hochberg MC. Epidemiology of the rheumatic diseases. 2nd edition: Oxford University Press; 2001.
Helmick CG, Felson DT, Lawrence RC et al. Estimates of the prevalence of arthritis and other rheumatic conditions in the United States. Part I. Arthritis & Rheumatism. 2008;58:15-25.
National Institutes of Health, National Institute of Arthritis and Musculoskeletal and Skin Disease. Handout on Health: Arthritis.