There are five distinct types of psoriatic arthritis (PA), each with its own characteristics:

• Asymmetric arthritis. The mildest form of PA. In most cases, it affects joints on only one side of the body or different joints on each side. Joints affected include those of the hip, knee, ankle or wrist, which may feel tender or become red. One to three joints are generally involved in asymmetric arthritis. Swelling and inflammation in the tendons can cause fingers and toes to resemble small sausages, a condition known as dactylitis.
  
  
• Symmetric arthritis. Usually affects four or more of the same joints on both sides of the body. It is similar to rheumatoid arthritis (RA) but usually milder. Symmetric arthritis can cause progressively disabling joint damage. Psoriasis associated with this condition, which affects women more often than men, tends to be severe.
  
  
• Spondyloarthropathy or spondylitis. Characterized by inflammation of the spine and stiffness and inflammation in the neck, lower back or sacroiliac joints. In some cases, inflammation can extend to where ligaments and tendons attach to the spine. Patients may find that movement becomes increasingly painful and difficult as the disease progresses. Other spondylarthropies (inflammatory conditions involving a gene called HLA-B27) include ankylosing spondylitis and Reiter's syndrome.
  
  
• Arthritis mutilans. A long-term, painful, crippling form of PA that affects a small percentage of people with the disease. As it progresses, arthritis mutilans destroys the small bones (a process called osteolysis) in the hands and fingers, causing permanent deformity and disability. This condition may cause the fingers and wrist to shorten, with skin folds around them (which is termed “opera glass hand”). This form tends to affect men more often than women.
  
  
• Distal interphalangeal joint predominant (DIP). Affects the small joints closest to the nails (distal interphalangeal joints) in the fingers and toes. DIP is among the least common forms of PA, and it tends to affect men more often than women. Some physicians misdiagnose DIP as osteoarthritis (arthritis that results from destruction of cartilage on the ends of the bones).

There is also a form of the disease that can affect children, juvenile psoriatic arthritis.