Psoriatic arthritis (PA)is one of the most common forms of inflammatory arthritis. Like its not so distant cousin, rheumatoid arthritis, PA is a systemic autoimmune driven form of arthritis. It is most common in people who have an extensive amount of psoriasis. According to the National Psoriasis Foundation, between 10 per cent and 30 per cent of people with psoriasis will develop PA. Interestingly, patients may develop the arthritis before they have clinical psoriasis.
Most patients with psoriatic arthritis, if joint symptoms are minimal, usually see a dermatologist before realizing they have PA. Symptoms include swelling, heat, redness, and pain involving not only the joints but the entheses (tendon attachments into the bone) as well. In addition, tendon sheaths in the fingers and toes can swell, causing what is termed a "sausage" digit. Stiffness in the morning is usually present.
Patients with PA can have variants of the disease. Some patients have more involvement of the spine than others. PA is typically non-symmetric as opposed to rheumatoid arthritis which tends to be symmetric in presentation. It is this asymmetry that can be useful for suspecting the diagnosis.
In addition to the typical rash of psoriasis, patients may have nail pitting or lifting up of the finger or toenail.
Like other autoimmune forms of arthritis, there is a systemic component to this disease. In particular, patients with PA can develop eye inflammation.
Imaging procedures such as magnetic resonance imaging (MRI) can help confirm the diagnosis. Specific changes at the entheses are characteristic of PA.
Treatment starts with making the diagnosis. Diseases that can be confused with PA are rheumatoid arthritis, gout (the serum uric acid can be elevated in patients with PA), fibromyalgia, pseudogout, ankylosing spondylitis, sarcoidosis, Lyme disease, and Reiter's disease.
The aims of proper therapy are to slow down the progress of the disease and restore function. A combination of an anti-inflammatory drug and a disease-modifying anti-rheumatic drug (DMARD) is the usual starting point of treatment. While methotrexate is the DMARD of choice for rheumatoid arthritis, it may not work quite as well in PA. Options include sulfasalazine (Azulfidine), leflunomide (Arava), and hydroxychloroquine (Plaquenil).
In patients who do not respond within eight to twelve weeks, biologic therapy using a TNF inhibitor is the next logical step. Among the options here are etanercept (Enbrel), infliximab (Remicade), adalimumab (Humira), and golimumab (Simponi).
Patients with a single inflamed joint or tendon may respond to steroid injection.