How Common is Psoriatic Arthritis?

Estimates vary on how many people with psoriasis go on to develop psoriatic arthritis (PsA), in part because the disease presents with a wide variety of symptoms among patients and diagnosis may be missed or delayed.1,2 Studies have shown that anywhere between 5 percent to 30 percent of people with psoriasis eventually develop psoriatic arthritis.3

On the other hand, 85 percent of people with PsA also have psoriasis.3 Reports of the incidence of psoriatic arthritis vary between 6 percent and 42 percent, noting that the lower estimates may reflect a missed diagnosis or misdiagnosis (receiving the wrong diagnosis, such as rheumatoid arthritis).2,4

Let's break down the prevalence of PsA

In one study that assessed the prevalence of PsA in 1,511 patients with psoriasis, 21 percent had existing PsA and 85 percent of those cases had been diagnosed for the first time during the course of the study.5

Psoriasis patients who were routinely treated at a dermatology clinic were evaluated by a rheumatologist in another study where 30 percent were diagnosed with PsA and 41 percent of those cases had not been aware of the diagnosis previously.2

Are there certain populations affected?

Psoriatic arthritis is thought to occur in up to 1 to 2 percent of the general population, with survey results indicating that approximately 1 million adults in the U.S. have PsA.4,6 Caucasians are known to be more commonly affected than African Americans and Native Americans. Men and women are equally affected.3 PsA generally develops in people aged 30-50 years, most often in the 40s and 50s. In the juvenile form of the disease, PsA develops at 9-11 years of age.3,6

Statistics on symptoms of psoriatic arthritis

  • Nail lesions occur in about 87 percent of people diagnosed with psoriatic arthritis.3
  • Inflammation causing a sausage-shape to the fingers or toes (dactylitis) occurs in up to 50 percent of people with PsA and is a marker for disease progression.2,3
  • Severe psoriatic arthritis, affecting four or more joints, occurs in about 20 percent of people living with PsA.3
  • Inflammation at attachment sites for tendons, ligaments, or joint fiber capsules (enthesitis) occurs in up to 50 percent of people living with PsA. It can also affect the eyes.3,6
  • Spinal or axial involvement, including inflammation between the vertebrae in the spine (spondylitis) and/or between the spine and the pelvis (sacroiliitis), occurs in up to 40 percent of people with PsA.8

Statistics on the progression of psoriatic arthritis

  • PsA is a progressive disease, and 55 percent of those living with the disease will develop five or more deformed joints in 10 years or more.4
  • Skin psoriasis precedes the onset of psoriatic arthritis (PsA) in 14 percent to 25 percent of patients with psoriasis. When skin symptoms occur first, it takes an average of 10-12 years for joint symtpoms to appear.7,8
  • In about 10 percent to 15 percent of cases, PsA will develop before psoriasis.2
  • It has been reported that there is a subset of patients with PsA who may achieve remission for at least 12 months. These cases tend to be men with a lower number of actively inflamed joints at diagnosis. However, after an average of 2.6 years, 52 percent of these patients had flares, and only 6 percent sustained a complete, prolonged remission without medications.4
  • PsA is severe in at least 20 percent of people living with the disease. Cases with severe disease are defined by the number of joints affected, usually four or more.4,8

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Written by: Emily Downward & Jessica Pool | Last reviewed: September 2019.