Psoriatic arthritis, or PsA, is a particular type of arthritis (joint inflammation) that develops in individuals with psoriasis, a skin condition that causes painful, itchy, and flaky skin rashes. Psoriatic arthritis can occur in any joint in the body. 30-50% of the 7.5 million Americans with psoriasis will develop psoriatic arthritis, and even fewer will develop severe forms of the condition.
Psoriatic arthritis is categorized by the location and severity of inflammation. There are five main types:
- Symmetric psoriatic arthritis. This is the most common type of psoriatic arthritis, accounting for about 50% of all cases. As its name “symmetric” suggests, this type of psoriatic arthritis affects both sides of the body equally, developing in opposing joints.
- Asymmetric psoriatic arthritis. This is the second most common type of psoriatic arthritis, accounting for about 30% of all cases. Asymmetric psoriatic arthritis does not affect each side of the body equally, and can occur in a random selection of joints.
- Distal psoriatic arthritis. In this type of psoriatic arthritis, inflammation occurs mainly in the nailbed region of the toes and fingers. Severe inflammation can cause the fingers and toes to swell, creating a “sausage-like” appearance. Nail discoloration, thickening, separation, or pitting often accompanies the swelling.
- This type of psoriatic arthritis refers to inflammation that is specific to the joints of the spine. Spondylitis can and often does occur along with other types of psoriatic arthritis
- Arthritis mutilans. This is a rare and especially damaging form of psoriatic arthritis that can lead to severe deformation of the hands and feet. Less than 5% of people with psoriatic arthritis will be diagnosed with arthritis mutilans.
Cases of psoriatic arthritis can be mild or severe.
- Oligoarticular psoriatic arthritis affects up to four joints.
- Polyarticular psoriatic arthritis affects more than four joints.