Psoriatic arthritis is a form of inflammatory arthritis that affects 10%-30% of the millions of Americans who have the skin condition psoriasis, according to the National Psoriasis Foundation. Psoriasis is an inflammatory skin disorder characterized by frequent episodes of redness and itching; thick, dry, silvery scales on the skin; and nail abnormalities.
There are five types of psoriatic arthritis. It is important to know which type of psoriatic arthritis you have and to understand its characteristics so it can be treated properly.
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
Symmetric Psoriatic Arthritis
Symmetric psoriatic arthritis affects the same joints -- usually in multiple matching pairs -- on both sides of the body. Symmetric psoriatic arthritis can be disabling, causing varying degrees of progressive, destructive disease in 50% of people with this type of arthritis. Though symmetric psoriatic arthritis resembles rheumatoid arthritis, it is generally milder.
Asymmetric Psoriatic Arthritis
Asymmetric psoriatic arthritis typically involves one to three joints in the body -- large or small -- such as the knee, hip, or one or several fingers. Asymmetric psoriatic arthritis does not affect matching pairs of joints on both sides of the body.
Distal Interphalangeal Predominant (DIP)
Distal interphalangeal predominant psoriatic arthritis involves primarily the small joints in the fingers and toes closest to the nail. DIP is sometimes confused with Heberden's nodes caused by osteoarthritis, a chronic disease that causes the deterioration of joint cartilage and tissues and bone spurs at the joints.
Spondylitis affects the spinal column, and may cause inflammation and stiffness in the neck, lower back, spinal vertebrae, or sacroiliac region (pelvic area), making motion difficult. Spondylitis also may attack connective tissue, such as ligaments, or cause arthritic disease in the joints of the arms, hips, legs, or feet.
Arthritis mutilans is a severe, deforming, and destructive form of psoriatic arthritis that primarily affects the small joints in the fingers and toes closest to the nail but also is frequently associated with lower back and neck pain. Fortunately, this type of psoriatic arthritis is uncommon.