Psoriatic Arthritis (PsA)

What is Psoriatic Arthritis? 

"Inflammatory arthritis" refers to a condition that causes joint pain, swelling, stiffness, and redness. Psoriatic arthritis (PsA) is an inflammatory arthritis that occurs mainly in people who have psoriasis. PsA affects around 30 percent of patients with psoriasis and approximately 500,000 Americans overall. 

PsA mainly affects the joints, but it can also affect the tendons (such as the Achilles tendon), particularly at the site where a tendon (or ligament) inserts into a bone (known as the enthesis). The pattern of joints involved and symptoms experienced in PsA varies considerably from person to person. Patients with PsA may have arthritis in the sacroiliac joints, which can lead to low back or buttock pain or stiffness. The cause of psoriatic arthritis is unknown. It can occur at any age, though it usually first appears between age 30 and 50. Women and men are affected equally.​

PsA is part of a larger group of arthritis types called spondyloarthritis. These include axial spondyloarthritis (also known as ankylosing spondylitis), reactive arthritis, inflammatory bowel disease-associated arthritis, and undifferentiated spondyloarthritis.

Symptoms of PsA and the Spondyloarthropathies

Signs and symptoms of PsA and the spondyloarthropathies include:

  • Joint swelling
  • Joint pain
  • Joint tenderness
  • Warmth of the joint
  • Stiffness of the joints, neck, or back upon awakening in the morning or after prolonged periods of rest or inactivity
  • Swelling, redness, and severe pain in an entire finger or toe, such that it looks like a sausage ("sausage digit" or dactylitis)
  • Fatigue

Diagnosing PsA and the Spondyloarthropathies

There is no one test that can diagnose PsA, but blood and imaging tests can sometimes aid in the clinical diagnosis. The CASPAR (ClASsification of Psoriatic ARthritis) criteria are often used to define psoriatic arthritis in clinical trials. However, some patients who do not meet these criteria may receive a clinical diagnosis.

These criteria require that a patient have inflammatory arthritis (swelling in the joint), enthesitis (inflammation where a tendon or ligament inserts into the bone) or spondylitis (inflammation in the spine), and at least three points from the following:

  • X-ray evidence of new bone formation in the hands or feet (excluding osteophytes, the type of new bone formation found in osteoarthritis) (1 point)
  • Evidence of current psoriasis (diagnosed by a rheumatologist or dermatologist) or personal history of psoriasis (2 points), OR family history of psoriasis (1 point)
  • Typical psoriatic nail dystrophy (pitting of the nails or breaking apart of the nails) on current physical examination (1 point)
  • Sausage digit (known as dactylitis) on exam or recorded by a rheumatologist (1 point)
  • Negative rheumatoid factor (1 point)