Psoriasis is a scaly rash that occurs most frequently on the elbows, knees, and scalp, but can cover much of the body. It is a chronic, inflammatory disease of the skin, scalp, nails, and joints. A normal skin cell matures and falls off the body’s surface in 28 to 30 days, but a psoriatic skin cell takes only three to four days to mature and gathers at the surface, thus forming lesions.
Up to 30 percent of people with psoriasis also develop psoriatic arthritis. In most cases (though not always), the psoriasis will precede the arthritis, sometimes by many years. When arthritis symptoms occur with psoriasis, it is called psoriatic arthritis (PsA). In these cases, the joints at the end of the fingers are most commonly affected, causing inflammation and pain, but other joints like the wrists, knees, and ankles can also become involved. This is usually accompanied by symptoms in the fingernails and toenails, ranging from small pits in the nails to nearly complete destruction and crumbling as seen in reactive arthritis or fungal infections.
About 20 percent of patients with PsA will develop spinal involvement, which is called psoriatic spondylitis. Inflammation of the spine can lead to complete fusion, as in ankylosing spondylitis (AS), or affect only certain areas such as the lower back or neck. Patients who are HLA-B27 positive are more likely than others to have their disease progress to the spine.
PsA and AS are considered genetically and clinically related because both are inflammatory rheumatic diseases linked to the HLA-B27 gene. HLA-B27 is a powerful predisposing gene associated with several rheumatic diseases. The gene itself does not cause disease, but can make people more susceptible. While a number of genes are linked to PsA, the highest predictive value is noted with HLA-B27.
The symptoms of PsA, which vary from person to person, can change in severity. Skin symptoms typically (but not always) appear before the joints become involved, sometimes up to 10 years before. Without treatment, many of these symptoms can lead to progressive, permanent joint damage.
Diagnosing psoriatic arthritis (PsA) can be tricky, primarily because it shares similar symptoms with other diseases such as osteoarthritis, rheumatoid arthritis, and gout. Because of this, misdiagnosis can often be a problem. Early diagnosis, however, is important because long-term joint damage can be warded off better in the first few months after symptoms arise.
The exact cause of psoriatic arthritis is not known, but it is known that heredity plays a large role. Up to 40 percent of people with PsA have a close relative with the disease. If an identical twin has PsA, there is a 75 percent chance that the other twin will have it as well.
Men and women are equally likely to develop psoriatic arthritis. PsA may strike at any age, but most commonly begins between the ages of 30 and 50. In children who develop PsA, the most common age of onset is 11 to 12.
Disease course and prognosis vary from individual to individual, and also depend on the form the disease takes. For example, someone who is HLA-B27 positive is more likely to have the disease progress to involve the spine.
Also, the severity of the rash does not mirror the severity of the arthritis, and the skin condition does not necessarily occur at the same time as the arthritis.
Although there is currently no known cure, there are treatments and medications available to reduce symptoms and manage the pain and inflammation caused by PsA.
The most common medications for PsA are often also used to treat ankylosing spondylitis, including nonsteroidal anti-inflammatory drugs (NSAIDs), disease-modifying antirheumatic drugs (DMARDs), sulfasalazine (Azulfidine), immunosuppressants, and biologic medications, such as TNF inhibitors.
Exercise is essential for preserving strength and maintaining range of motion in patients with PsA. Isometric exercises, which contract muscles without joint motion, may be less damaging to inflamed joints. Physical and occupational therapy may greatly help patients maximize the function of arthritic joints.
Patients should consult with their physician to determine which of these treatments is most appropriate for their condition.
While PsA can certainly affect an individual’s quality of life, the symptoms of the disease can be managed effectively. Paying attention to symptoms of the disease and addressing them as soon as they arise are important in achieving positive outcomes.
There are five distinct types of PsA:
Symmetric PsA affects the same joints in multiple matching pairs on both sides of the body, can be disabling, causing varying degrees of progressive joint destruction and loss of function.
Oligoarticular (asymmetric) PsA affects only a few joints but not matching pairs on opposite sides of the body, is often a milder form of the disease.
Distal interphalangeal predominant PsA primarily affects the joints closest to the toenails and fingernails, is sometimes confused with osteoarthritis.
Psoriatic spondylitis affects the spine anywhere from the neck to the lower back.
Arthritis mutilans, a rare but severe, destructive form of the disease leads to loss of joint function.
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