Pseudogout is a condition where crystals of calcium gather in and around a joint, often the knee, and cause pain.
The crystals are formed of calcium pyrophosphate, or CPP, and pseudogout is also known as acute CPP crystal arthritis. This is also referred to as a calcium crystal disease.
The reason for CPP crystals forming isn't fully known. It may be because of abnormal 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 surgery. The abnormal formation of CPP crystals may also be inherited.
What are the symptoms of pseudogout?
The symptoms of pseudogout are similar to symptoms of several other diseases, especially gout. Some symptoms of pseudogout are similar to those of rheumatoid arthritis or osteoarthritis. Symptoms of pseudogout include:
- Sudden, intense joint pain.
- Swollen joint that's warm to the touch.
- Red or purple skin around the joint.
- Severe tenderness around the joint (even the slightest touch or pressure may bring extreme pain).
Less often, pseudogout may cause persistent swelling, warmth and pain in several joints, and can even mimic rheumatoid arthritis.
Most symptoms of pseudogout go away within five to 12 days, even without treatment.
Who gets 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.
It also is commonly seen in people who have osteoarthritis, and "attacks" of osteoarthritis associated with pain, swelling and redness of the joint may in fact be due to pseudogout.
It is unusual for young people to develop pseudogout.
How frequently do pseudogout attacks occur?
Like gout, pseudogout attacks can recur from time to time in the same joint or in different joints. The initial attack may last five to 12 days unless it is treated. Unlike gout, attacks are not linked to certain foods in your diet.
Over time, pseudogout attacks may increase, involve more joints, cause more severe symptoms and last longer. Frequency of attacks is variable. Attacks may occur from once every few weeks to less than once a year. Frequent, repeated attacks can damage the affected joints.
How is pseudogout diagnosed?
Pseudogout cannot be diagnosed simply from a blood test. An X-ray of the joint can be taken to look for the presence of calcium containing crystals. To diagnose the condition, fluid is removed from the inflamed joint and analysed under a microscope. The presence of CPP crystals indicates pseudogout.
Fluid is removed through a needle from the inflamed joint in a procedure called "arthrocentesis". Removing the fluid also may help reduce the pressure within the joint and thereby reduce pain.