Psoriatic Arthritis

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Category: Inflammatory Spondyarthropathy Published on Wednesday, 25 June 2008 Written by Yong Tsai, MD
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Do you have itchy, scaly skin on your elbows, knees, scalp, navel or ears? Do your fingernails and toenails sometimes lift up? Do your joints and surrounding tendons swell? Do your fingers resemble little sausages? Well, you just might have psoriatic arthritis.

Psoriatic arthritis is a chronic inflammatory and autoimmune disease, which occurs when our immune system mistakes our own joint tissue for a foreign invader, attacking it and causing inflammation. When the inflammatory process advances, chemical mediators released from white blood cells damage cartilage, bone and ligaments causing joints to become deformed and impairing function. 

PSORIASIS’ ROLE IN PSORIATIC ARTHRITIS:

Psoriasis, named after the Greek word “psora” meaning “itching”, is characterized by a scaly, itchy skin rash, often on the elbows, knees, scalp, behind the ears, or on the navel. Psoriasis is a very common skin condition and occurs in one to two percent of Caucasians. Although it may develop at any age, it most commonly occurs in the late teens. Furthermore, about ten percent of those who suffer with psoriasis will develop psoriatic arthritis (PsA).

Usually, if you have psoriatic arthritis, you would develop psoriasis in your late teens, followed by arthritis in your thirties or forties. However, some patients do develop arthritic symptoms prior to psoriasis and some patients develop both at the same time.

Even though the exact cause of psoriatic arthritis is not yet fully understood, studies have shown that it can affect both genders equally. In addition, genetic predisposition, infection, trauma and other environmental triggers play an important role in the cause of PsA. 

COMMON SYMPTOMS:

About 95% of people with psoriatic arthritis experience swelling of the hand, wrist, elbow, knee, ankle, foot joints and their surrounding tendons. Such swelling gives fingers and toes a sausage-like appearance, which makes grasping an object or making a fist very painful. PsA also frequently affects tendons such as the Achilles tendon (in the heel) or plantar fascia (in the sole of the foot). Patients experience pain in the heels or bottoms of feet, particularly in the morning when taking their first steps.

The other five percent of people with psoriatic arthritis have inflammation of the spinal joints. This form of psoriatic arthritis most commonly affects joints in the neck, lower back and sacroiliac joints (tailbone area). Patients suffer pain and stiffness in the neck, lower back and buttocks that is worse at night and first thing in the morning. A common complaint with psoriatic arthritis of the spine is that patients usually are awakened at night due to an increase in pain. 

PSORIATIC VS. RHEUMATOID ARTHRITIS:

Even though psoriatic arthritis (PsA) may resemble rheumatoid arthritis (RA), in general, patients with PsA test negatively for rheumatoid factor, a blood test that is commonly positive with RA. The pattern of joint involvement is different for PsA and RA and occasionally, people with psoriasis can also have RA. Furthermore, RA affects three times more women than psoriatic arthritis, which equally affects both women and men.

While the course of psoriatic arthritis varies, most people do reasonably well and are able to lead productive lives. However, in about twenty percent of people, this disease may become deforming and destructive. In general, while PsA causes less long-term disability than does RA, fifteen percent of patients with PsA will become severely disabled, which warrants aggressive treatment to prevent joint damage. 

TREATMENT:

Since corticosteroids were discovered in 1948, its long-term side effects and inability to prevent bone and joint damage have tarnished its reputation, forcing scientists and physicians to explore new treatment options.

Over the years, studies have demonstrated that Methotrexate (MTX), Leflunomide and Sulfasalazine are effective in treating PsA and RA. Because these drugs affect the activity of PsA and RA to a greater extent than drugs such as aspirin or other non-steroidal anti-inflammatory drugs (NSAIDs), they appear to modify our body's immune system in some way that helps slowdown the inflammatory process. Therefore, this group of drugs was named disease-modifying anti-rheumatic drugs (DMARDs).

Recently, the strategic plan in treating PsA has changed from a conventional process of using NSAIDs and corticosteroids to control symptoms, to a more biological modifying process by adding DMARDs to the preceding in hopes of altering the inflammatory process and preventing joint damage.

In the past few years, due to breakthroughs in genetic engineering and a better understanding of chemical mediators in inflammation, tumor necrosis factor-alpha (TNF-alpha) and Interleukin-1 (IL-1) have proven to be the key chemical mediators, which initiate, maintain and perpetuate inflammation and cause joint damage. Therefore, blocking these key chemical mediators can impede and even prevent joint pain and damage. 

Three such drugs, which have been approved by FDA for treatment of RA, are Etanercept (Enbrel), Infliximab (Remicade) and Anakinra (Kineret), which through different chemical actions make TNF or IL-I molecules unavailable for use in the inflammatory process. As a result, these drugs impede the inflammatory response, ease joint pain and swelling and effectively slow down bone and cartilage damage. Recently, Enbrel has been approved for treating PsA and Remicade has been proven to be effective for patients with PsA.

Even though severe PsA is a debilitating disease, these new drugs give us good reason to be optimistic. If it is treated early and properly, joint pain and swelling can be controlled and deformities can be prevented or minimized.

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