Some kinds of arthritis are autoimmune disorders. This means your body's immune system makes chemicals that attack and damage your own tissues. This can cause enthesitis. It's a common symptom of two kinds of autoimmune arthritis -- psoriatic arthritis and ankylosing spondylitis. Psoriatic arthritis, which is common in people with the skin condition psoriasis, can affect your entire body. Ankylosing spondylitis mainly affects your spine.