What is pseudogout?

Pseudogout is a form of arthritis that causes pain, stiffness, tenderness, redness, warmth, and swelling (inflammation) in some joints. It usually affects one joint at a time, but sometimes it may affect several joints at once.

Pseudogout commonly affects the knee or wrist. Less often, it can involve the hips, shoulders, elbows, knuckles, toes, or ankles.

The symptoms of pseudogout are similar to the symptoms of other diseases, especially gout (which is why this form of arthritis is called pseudogout – “false gout”). Some symptoms of pseudogout are similar to the symptoms of rheumatoid arthritis or osteoarthritis.

Who is affected by pseudogout?

Pseudogout affects both men and women. Like gout, pseudogout occurs more frequently in people as they age, commonly affecting people over age 60.

People who have a thyroid condition, kidney failure, or disorders that affect calcium, phosphate, or iron metabolism have an increased risk for pseudogout. Pseudogout is also commonly present in people who have osteoarthritis. "Attacks" of osteoarthritis associated with pain, swelling, and redness of the joint may in fact be due to pseudogout.

Pseudogout in young patients is unusual. Its occurrence should lead the doctor to look for certain metabolic and hereditary disorders.

What are the symptoms of acute pseudogout?

  • Sudden, intense joint pain
  • Swollen joint that's warm and tender to touch
  • Red or purple skin around the joint

Less often, pseudogout may cause persistent swelling, warmth, and pain in several joints, and can even mimic rheumatoid arthritis.

What causes pseudogout?

Pseudogout results from the abnormal formation of calcium pyrophosphate (CPP) crystals in the cartilage ("cushion" between the bones), which is later followed by the release of crystals into the joint fluid (synovial fluid). When CPP crystals are released into the joint, they can cause a sudden attack of arthritis, similar to gout.

The cause of abnormal deposits of CPP crystals in cartilage is often unknown. They may form due to abnormal properties of cells in the cartilage, or they may be produced as the result of another disease that damages cartilage. CPP crystals may be released from cartilage during a sudden illness, joint injury, or previous surgery. The abnormal formation of CPP crystals may also be a hereditary trait.