Psoriasis is an autoimmune disease that causes an overproduction of skin cells, resulting in a variety of symptoms depending on the type of psoriasis and the severity of the condition. The most common type of psoriasis is plaque psoriasis, which causes patches of inflamed, scaly skin that are often itchy and sometimes painful.
An estimated 20 to 30 percent of people who have psoriasis have an associated autoimmune disease called psoriatic arthritis, otherwise known as PsA. With PsA, an overactive immune response triggers inflammation in the joints, causing pain, stiffness, swelling and tenderness to the touch. Long term, the disease can be debilitating, causing permanent damage to the joints and loss of mobility.
There are several forms of PsA, and these forms can overlap and change over time. Classification for these different forms takes into account a number of criteria, including how many joints are affected, which joints are affected and the severity of the symptoms.
Oligoarticular
“Oligo” is derived from a Greek prefix meaning “few.” Oligoarticular PsA affects four joints or fewer and usually has an asymmetrical pattern—meaning it affects a joint on one side of the body without affecting the same joint on the other. For example, you might have pain and swelling in your left elbow, but not your right. Symptoms of oligoarticular PsA tend to be mild. However, PsA is a progressive disease, and symptoms can worsen over time.
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Polyarticular
In cases where symptoms affect more than four joints, psoriatic arthritis can be described as “polyarticular.” This form can affect joints in either an asymmetrical pattern, or a symmetrical pattern, where symptoms are spread evenly across both sides of the body.
Distal interphalangeal Phalangeal (DIP)
DIP is a form of PsA that affects the distal joints, or the joints nearest to the tips of the fingers and toes. Symptoms like swelling, pain and tenderness are often accompanied by symptoms of nail psoriasis, such as pitting, discoloration and thickened layers of skin under the nail bed. DIP can have an asymmetrical or a symmetrical pattern, and may affect one or two distal joints, or many.
Spondylitis
PsA can cause spondylitis, inflammation of the joints that connect the vertebrae of the spinal column. Stiffness and pain in the neck, between the shoulder blades and the lower back are all symptoms of spondylitis. Over time, the inflammation in the spine can cause vertebrae to fuse together.
PsA can also inflame the joints between the spine and the pelvis—the sacroiliac joints—which is called sacroiliitis. Together, spondylitis and sacroiliitis are sometimes called “axial arthritis,” because they affect the joints of the axial skeleton.
Psoriatic arthritis mutilans
This is the most serious form of PsA, and it is relatively rare, occurring in only a small percentage of people who have PsA. Psoriatic arthritis mutilans typically affects the hands, though it can affect joints in other parts of the body. Severe inflammation destroys bone tissue, leading to bone loss and deformity.
If you have PsA or psoriasis
If you have been diagnosed with PsA, or you have been diagnosed with psoriasis and are experiencing pain, stiffness or swelling in your joints, it’s important to speak to your healthcare provider. While there is no cure for psoriatic arthritis, there are treatments that can help control symptoms, help improve joint functioning and help prevent further damage.