Americans are estimated to have psoriasis, and 10-30% of those people also develop psoriatic arthritis.
Psoriatic arthritis usually develops between the ages of 30 and 50.
of those diagnosed with psoriasis had not received a previous PsA diagnosis, suggesting underdiagnosis of patients in dermatologic practices.
What is psoriatic arthritis (PsA)?
Psoriatic arthritis is an autoimmune condition. Autoimmune conditions occur when the body’s immune system mistakes its own tissues for foreign invaders, such as bacteria or viruses. The confused immune system springs into action, seeking out to destroy the “invaders” in the tissues.
In the case of psoriatic arthritis, the immune system attacks healthy cells and tissue. This results in chronic joint pain and inflammation and the overproduction of skin cells.
Psoriatic arthritis is a form of arthritis that affects people who have psoriasis, which is a skin condition that involves your white blood cells mistakenly attacking your skin cells. This attack results in your body’s overproduction of skin cells, which is what causes the common symptom of psoriasis: red, scaly patches on the skin.
Who is affected?
Anyone can be diagnosed with psoriatic arthritis. The condition is generally diagnosed between the ages of 35 and 45. 
Doctors aren’t sure about what causes psoriatic arthritis, but believe that a combination of genetics and environment are responsible. Other factors like family history, physical trauma, and medical conditions like psoriasis may influence your level of risk as well. 
What happens in your body?
Common symptoms of psoriatic arthritis include: 
- Stiffness, pain, and tenderness in one or more joints
- Swollen fingers and toes, which can resemble sausages
- Lower back pain
- Small depressions in the nails or detachment from the nail bud
Symptoms of psoriatic arthritis can resemble other conditions, such as rheumatoid arthritis. But some aspects of psoriatic arthritis that are different from other conditions are pitting or flaking nails and tenderness in the soles or heels of your feet.
The condition can affect joints on one or both sides of the body. 
How do I know if I have psoriatic arthritis (PsA)?
It is important to get an accurate diagnosis as quickly as possible to make sure that the condition does not worsen. The best way to do this is by visiting your doctor and, if possible, getting a referral to visit a rheumatologist, a doctor with specialized training in treating psoriatic arthritis.
Some ways that your doctor can assess whether you have the condition is through a physical examination or lab tests (such as imaging tests).