Psoriatic arthritis (PSA)

Definition

Psoriatic arthritis (PSA) is an inflammatory condition that affects the joints of children and adults with psoriasis. Psoriasis is a skin condition that causes patches of thick, red skin to form on certain areas of your body. Not everyone with psoriasis develops psoriatic arthritis, but everyone with psoriatic arthritis has psoriasis.

Most people develop the skin signs of psoriasis first and are later diagnosed with psoriatic arthritis. Joint pain in people with psoriatic arthritis can range from mild to severe. Many experience changing signs and symptoms as the disease continues.

Many definitions of psoriatic arthritis exist, which makes it hard to estimate how many people have the disease. About 10 percent to 15 percent of people with psoriasis eventually develop psoriatic arthritis. While no cure for psoriatic arthritis exists, doctors work to control your signs and symptoms and prevent damage to your joints.

Symptoms

Psoriatic arthritis may affect one joint or many. Signs and symptoms of psoriatic arthritis include:

• Pain in affected joints
• Swollen joints
• Joints that are warm to the touch

Patterns of joint pain in psoriatic arthritis

Doctors have identified five patterns in which psoriatic arthritis typically occurs. Most people move from one pattern of psoriatic arthritis to another throughout their lives. Treatment usually varies based on the pattern of joint involvement you experience. Patterns of psoriatic arthritis include:

• Pain in joints on one side of your body. The mildest form of psoriatic arthritis, called asymmetric psoriatic arthritis, usually affects joints on only one side of your body or different joints on each side – including those in your hip, knee, ankle or wrist. One to three joints are generally involved, and they're often tender and red. When asymmetric arthritis occurs in your hands and feet, swelling and inflammation in the tendons can cause your fingers and toes to resemble small sausages (dactylitis).
• Pain in joints on both sides of your body. Symmetric psoriatic arthritis usually affects four or more of the same joints on both sides of your body. More women than men have symmetric psoriatic arthritis, and psoriasis associated with this condition tends to be severe.
• Pain in your finger joints. Distal interphalangeal (DIP) joint predominant psoriatic arthritis is rare and occurs mostly in men. DIP affects the small joints closest to the nails (distal joints) in the fingers and toes.
• Pain in your spine. This form of psoriatic arthritis, called spondylitis, can cause inflammation in your spine as well as stiffness and inflammation in your neck, lower back or sacroiliac joints. Inflammation can also occur where ligaments and tendons attach to your spine. As the disease progresses, movement tends to become increasingly painful and difficult.
• Destructive arthritis. A small percentage of people with psoriatic arthritis have arthritis mutilans – a severe, painful and disabling form of the disease. Over time, arthritis mutilans destroys the small bones in the hands, especially the fingers, leading to permanent deformity and disability.

Causes

Psoriasis is a skin condition marked by a rapid buildup of rough, dry, dead skin cells that form thick scales. Arthritis causes pain and stiffness in your joints. Both are autoimmune problems – disorders that occur when your body's immune system, which normally fights harmful organisms such as viruses and bacteria, begins to attack healthy cells and tissue. The abnormal immune response causes inflammation in your joints as well as the overproduction of skin cells.

It's not entirely clear why the immune system turns on itself, but it seems likely that both genetic and environmental factors play a role. Many people with psoriatic arthritis have a close relative, such as a parent or sibling, with the disease, and researchers have discovered certain gene mutations that appear to be associated with psoriatic arthritis.

Having a genetic mutation doesn't necessarily mean you'll develop psoriatic arthritis, but it does mean you have a greater tendency to do so than other people do. Physical trauma or something in the environment – such as a viral or bacterial infection – may eventually trigger psoriatic arthritis in people who have an inherited tendency.

Risk factors

Having psoriasis is the single greatest risk factor for psoriatic arthritis. In particular, people who experience psoriasis lesions on their nails are more likely to develop psoriatic arthritis.

Other risk factors include:

• Family history. Many people with psoriatic arthritis have a close relative with the disease.
• Age. Although anyone can develop psoriatic arthritis, it occurs most often in adults between the ages of 30 and 50.
• Sex. In general, psoriatic arthritis affects men and women equally, but DIP and spondylitis are more likely to affect men, whereas symmetric arthritis occurs more often in women.

Source: Mayoclinic.com