Not everyone who has psoriasis will get psoriatic arthritis, even though the conditions are often related.
Psoriasis causes patches of scaly, red, or white skin called plaques. Psoriatic arthritis sets off joint swelling and pain that can lead to permanent damage. Your immune system is responsible for both.
How They’re Connected
Inflammation is part of both psoriasis and psoriatic arthritis. Both of these conditions occur because your immune system attacks your own body instead of something foreign to you.
A little less than a third of people who have psoriasis will get psoriatic arthritis. Doctors can’t yet tell who before it happens, though.
Usually, you’ll have the skin symptoms first. But sometimes, arthritis symptoms appear months, or even years, before skin problems do. That makes it hard to diagnose.
People with severe psoriasis could have a greater chance of getting psoriatic arthritis.
Psoriasis skin plaques can flare up and then get better. Psoriatic arthritis symptoms may also come and go.
About 40% of people who get psoriatic arthritis have relatives with it or with psoriasis. Scientists don’t know which genes are responsible for these conditions. Figuring that out will help doctors predict who is likely to get these conditions. It may lead to new treatments, too.
How They’re Different
There’s no connection between the location of your plaques and which joints are affected. For example, you could have:
- Skin lesions on your elbow, but no pain, no swelling, and no problems bending and moving it
- Swollen toes, but no redness or scales on your feet
Psoriasis doesn’t cause scarring or any other lasting harm to skin. But psoriatic arthritis can damage joints and leave them stiff and deformed if it isn’t treated.
That’s why you need to work with your doctor even if your symptoms get better. Don’t stop taking medications unless your doctor says it’s OK.
- American College of Rheumatology: “Psoriatic arthritis."
- National Psoriasis Foundation: “Psoriatic arthritis."
- Philip Mease, MD, Seattle Rheumatology Associates.
- John Hardin, MD, chief scientific officer, Arthritis Foundation; professor of medicine, Albert Einstein College of Medicine, New York City.
- Arthritis Foundation: “Psoriatic arthritis."
- Mark Lebwohl, MD, professor and chairman of dermatology, Mount Sinai School of Medicine.
- The Johns Hopkins Arthritis Center: “Psoriatic arthritis," “New Onset Psoriatic Arthritis Reported in Psoriasis Patients Treated with Efalizumab."
- Viguier, M. Arthritis Rheum, May 2008.