How common is psoriatic arthritis?
One in every five patients with psoriasis develops psoriatic arthritis. However, as noted above, some patients with psoriasis are more likely to experience this problem. One of the most important risk factors is the severity of the skin disease.
According to statistics, 54.9% of patients with severe psoriasis progress to psoriatic arthritis. That is more than half. In moderate psoriasis, 35% of the patients develop these joint manifestations, and the incidence is 9.9% in patients with mild psoriatic arthritis.
In the United States, the incidence of psoriatic arthritis is 30% in people with psoriasis, which is close to 1 million people. However, other studies report different statistics, and the exact frequency is 5-30% depending on the study and the population.
Worldwide, the incidence of psoriatic arthritis is 133 patients per 100,000 population. That is to say that one in four patients with a diagnosis of psoriasis develops psoriatic arthritis. The incidence is exceptionally high in sub-Saharan Africa, especially among people with HIV.
The age of onset is usually between 35 and 55 years. There is also a juvenile form of psoriatic arthritis in patients aged 9-11 years. It is more prevalent in whites, but African Americans usually have worse symptoms if they develop the disease.