Up to 30% of people with psoriasis also develop psoriatic arthritis. In psoriatic arthritis, joints become sore, stiff, and swollen. Untreated psoriatic arthritis can even cause permanent joint damage.
Psoriatic arthritis can affect almost any joint and can masquerade as other forms of arthritis. Treatment can improve symptoms and might prevent long-term damage from psoriatic arthritis.
Everyone with psoriatic arthritis has both skin and joints affected, at some point. Most people have recognized psoriasis, followed by arthritis. In about 15% of people with psoriatic arthritis, the arthritis comes first, with no initial skin involvement. Another 15% with psoriatic arthritis have skin lesions preceding arthritis, but don’t recognize them as psoriasis.
The symptoms of psoriatic arthritis include:
Pain, stiffness and swelling in joints
Stiffness that’s worse after being still, and better after moving
Psoriatic arthritis can affect other areas besides joints:
Tendons, at the attachment point to bone.
Fingers and toes, which can swell into “sausage digits.” Swelling can also affect the whole hand or foot.
Fingernails and toenails, with pitting or crumbling of nails.
Psoriatic arthritis varies in severity. In some people, psoriatic arthritis causes mild aches and pains. Others are affected more severely. Psoriatic arthritis can be destructive to joints and even cause deformities or disability. In this aspect, psoriatic arthritis is similar to rheumatoid arthritis, although usually milder.
Is it Psoriatic Arthritis, or Psoriasis and Arthritis?
Not everyone with psoriasis and arthritis has psoriatic arthritis. People with psoriasis can develop other forms of arthritis, just like anyone else. The most common kinds of arthritis are:
Osteoarthritis, the most common kind of arthritis overall. This is the “wear and tear” arthritis caused by aging and injury.
Gout, arthritis characterized by attacks that occur when crystals deposit in the joints. Gout attacks are intensely painful, then subside over days.
Rheumatoid arthritis, an autoimmune disease of the joints. Psoriatic arthritis is also an autoimmune disease, but is different from rheumatoid arthritis.
Diagnosis of Psoriatic Arthritis
There is no single test that accurately diagnoses psoriatic arthritis. Instead, doctors make the diagnosis of psoriatic arthritis based on all the available information taken together. Some tests a doctor might order to diagnose psoriatic arthritis include:
Lab tests: anti-nuclear antibody (ANA), rheumatoid factor (RF), or anti-cyclic citrullinated peptide (anti-CCP) may be elevated in psoriatic arthritis.
Joint aspiration: Using a needle to withdraw fluid from a swollen joint can rule out gout and some other forms of arthritis.
Radiology: Plain X-rays or magnetic resonance imaging (MRI) can identify joint damage caused by psoriatic arthritis and help differentiate it from other forms of arthritis.
If a doctor finds typical X-ray findings of psoriatic arthritis, psoriasis on the skin, and no other type of arthritis, it’s enough to make the diagnosis in most people with psoriatic arthritis. A rheumatologist (joint specialist) may be the most qualified to make the diagnosis of psoriatic arthritis.