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Psoriatic Arthritis and Psoriasis: What's the Connection?

By Hilary Parker
WebMD Feature

What's the connection between psoriasis and psoriatic arthritis? Both are thought to be caused primarily by your immune system. But not everyone who has psoriasis -- which causes patches or plaques of scaly and inflamed skin -- develops psoriatic arthritis. This form of inflammatory arthritis causes joint swelling and pain, and may lead to permanent deformity and damage if not treated.

Symptoms of Psoriatic Arthritis

Some of the most common psoriatic arthritis symptoms include:

  • Painful, swollen joints: Psoriatic arthritis can be symmetrical (meaning it affects the same joints on both sides of the body) or asymmetrical. With asymmetrical psoriatic arthritis, your left fingers and right toes might be affected, for example.
  • Sausage-like swelling of fingers and toes  
  • Nail changes: Psoriatic arthritis often affects the joints closest to the nail bed. It can cause pitting or ridging of the nails or nails that peel away from the fingers and toes.
  • Fatigue
  • Back and neck pain: For about 5% of people with psoriatic arthritis, the main symptom is an inflamed spinal column, which makes movement very difficult.  
  • Stiffness, especially after sitting or sleeping  
  • Conjunctivitis  

How Psoriasis and Psoriatic Arthritis Are Connected

About 30% of people who have psoriasis will develop psoriatic arthritis. In most cases, the skin symptoms of psoriasis appear before psoriatic arthritis develops. It is possible, however, for psoriatic arthritis symptoms to appear months, or even years, before any skin lesions develop.   

Both psoriasis and psoriatic arthritis are thought to be caused by primarily by your immune system. In the case of your skin, this causes cells to grow too quickly without sloughing off. Layers of skin build up, resulting in the skin plaques of psoriasis. With psoriatic arthritis, the immune system targets joints and connective tissue, causing destructive, painful, swollen joints.

There does not seem to be a connection between where the scaly skin patches from psoriasis are located and which joints are affected by psoriatic arthritis. For example, you could have skin lesions on both your elbows, but your elbow joints could be unaffected by psoriatic arthritis. In the same way, psoriatic arthritis could cause sausage-like swelling of the toes without any redness or scaling on the feet.  

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What psoriatic arthritis symptom bothers you most?