Diseases > Calcium Pyrophosphate Deposition Disorder (CPPD) > What is it?
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What is CPPD?
Calcium pyrophosphate deposition disorder (CPPD) is a form of arthritis (rheumatological disease). It results from the formation of calcium pyrophosphate crystals around the joints and tendons. These crystals can be present in the knees, wrists, pelvis, elbow, shoulder, knuckles and other joints.
CPPD is a bit like a chameleon. It can mimic symptoms of many other arthritic diseases including gout, osteoarthritis, rheumatoid arthritis, and tendonitis. This can make the diagnosis of CPPD a little tricky!
Gout is caused by a build-up of crystals in the joints. In gout, these crystals are made up of uric acid. When uric acid crystals form in a joint the immune system attacks them causing severe pain, redness, and swelling. In CPPD, the crystals are made up of calcium pyrophosphate. When calcium pyrophosphate crystals form suddenly inside a joint the immune system can attack them as well. This results in a joint that is very painful, red, and swollen just like gout. For this reason, CPPD is sometimes known as pseudogout.
CPPD can be also associated with osteoarthritis (OA). Calcium pyrophosphate crystals can build up in joints that are typically affected by OA such as the knees. They can also build up in joints that are not typically affected by OA such as the wrists, pelvis, elbows and shoulders. If a joint looks like it is affected by osteoarthritis but it isn’t in a typical location for OA it might be CPPD.
When CPPD affects joints in the hands (knuckles) it can be mistaken for rheumatoid arthritis (RA). The knuckles can be swollen, painful and stiff, just like RA. But an X-ray of the hand will not show changes that would typically be expected with RA.
CPPD can also cause calcification of the tendons and ligaments. This typically affects the tendons around the shoulder joints (rotator cuff) and the achilles tendon (the heels). This can be severe and debilitating.
What causes CPPD?
CPPD is caused by a build-up of calcium pyrophosphate crystals in the joints and tendons throughout the body. We do not know why these crystals form. As far as we know, taking calcium supplements does not cause CPPD or make it worse.
Who gets CPPD?
CPPD typically affects men and women over the age of 50. There can be other diseases associated with CPPD. These include hypothyroidism (underactive thyroid gland), hyperparathyroidism (overactive parathyroid gland), hypomagnesemia (low magnesium) or hemochromatosis (too much iron in the body).
How is CPPD diagnosed?
CPPD can be difficult to diagnose because of its chameleon-like nature. A rheumatologist – a specialist in arthritis and autoimmune diseases – is the best position to diagnose the disease. Your rheumatologist will take a complete history and perform a thorough physical examination. This is usually followed by blood tests, X-rays and other types of tests.
What tests are done to diagnose CPPD?
The first step to help diagnose CPPD is a thorough history and a complete physical examination by an arthritis specialist (rheumatologist). X-rays can then be very useful to see typical features of CPPD. Sometimes a sample of fluid from an affected joint can be used to the confirm diagnosis of CPPD. Sometimes an ultrasound can show calcium build-up in the tendons. Blood tests are used to look for conditions associated with CPPD including levels of thyroid hormone (TSH), parathyroid hormone (PTH), iron (ferritin) and magnesium.
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