Calcium pyrophosphate is a substance produced in the cartilages of the joints. It can become deposited as crystals on joint tissues. This is called calcium pyrophosphate deposition. Calcium pyrophosphate deposition can cause a number of problems of which the most well known is pseudogout. This is almost identical to gout, causing attacks of pain and swelling in one or more joints. Some people develop damage to the joint, causing a type of long-term arthritis. Calcium pyrophosphate deposition may cause no symptoms and is sometimes picked up on an X-ray done for an unrelated condition. Unlike gout, there is no special treatment for pseudogout. Rest, ice packs and anti-inflammatory medicines are the main forms of treatment.
What is calcium pyrophosphate deposition (CPPD)?
Calcium pyrophosphate (CPP) crystals can become deposited on cartilage and various other tissues in and around joints. This is known as CPP deposition (CPPD). Some people have CPPD on the cartilages that cover their joints. This is known as chondrocalcinosis. It may cause no symptoms but may be picked up on an X-ray. Other people may have an attack of joint pain and swelling identical to gout. This is called pseudogout, or acute CPP crystal arthritis. There is also a longer-term condition called chronic CPP crystal inflammatory arthritis. Some people with osteoarthritis get CPPD and, when this causes symptoms, it is referred to as osteoarthritis with CPPD.
Why are CPP crystals formed?
There can be many reasons why CPP forms crystals which settle on the tissues in and around the joints.
Some people inherit a fault in one of the basic units of genetic information (a gene) which makes them more prone to develop CPP crystals in the joints.
Several conditions can trigger crystal formation, including:
- Lack of fluid (dehydration).
- An attack of any severe illness.
- Overactivity of the parathyroid glands (hyperparathyroidism).
- Long-term use of steroid medicine.
- Underactive thyroid gland (hypothyroidism).
- Any cause of arthritis.
- An illness which causes too much iron in the body (haemochromatosis).
- An inherited illness causing a build-up of copper in the body (Wilson's disease).
- An illness caused by an increased level of growth hormone in the body (acromegaly).
- Kidney dialysis.
- Surgery or injury.
- Low magnesium level in the blood (hypomagnesaemia).
How common is calcium pyrophosphate deposition (CPPD)?
CPPD is more common as you get older. X-ray studies show that over half of people over the age of 80 have changes typical of CPPD. One English study calculated that 7-10 people out of 100 over the age of 60 have CPP crystals which accumulate on cartilage (chondrocalcinosis). Men and women are equally affected.
Figures from America suggest that every year about 1 in 100,000 people experience an acute attack of pseudogout,
What are the symptoms of calcium pyrophosphate deposition (CPPD)?
CPP crystals which accumulate on cartilage (chondrocalcinosis) may cause no symptoms but may just be picked up on an X-ray.
Acute CPP crystal arthritis, or pseudogout, may cause exactly the same symptoms as gout. Thus, there will be pain, warmth, redness and swelling of one or more joints. Any joint can be involved but the knees are most commonly affected, followed by the wrists, shoulders, ankles, hands and feet.
Chronic CPP crystal arthritis resembles osteoarthritis. It causes longer-term damage to joints, with pain and stiffness. Knees, hips, shoulders and wrists are most often affected.
How is calcium pyrophosphate deposition (CPPD) diagnosed?
X-rays may be helpful. They show shadows that look like straight lines typical of chondrocalcinosis. Scans may also be useful. Looking at joint fluid that has been removed with a syringe and needle under the microscope may show typical CPP crystals.
Tests may be needed to rule out other causes.
What else could it be?
What is the treatment for calcium pyrophosphate deposition (CPPD)?
Chondrocalcinosis which produces no symptoms does not need any treatment.
Pseudogout cannot be cured but treatment is available to relieve the symptoms until the attack settles. Ice packs and rest may be helpful. Painkillers and anti-inflammatory medicines are usually given to help the pain and inflammation. Other treatments sometimes tried include draining any fluid with a syringe and needle, injecting steroid liquid into the joint and taking steroid tablets.
Chronic CPP crystal arthritis is usually treated in the same way as pseudogout, with painkillers and anti-inflammatory medicines. Other medicines tried are called colchicine, methotrexate and hydroxychloroquine.
What is the outlook (prognosis)?
Attacks of pseudogout usually settle in about ten days. Chronic CPP crystal arthritis can cause long-term joint damage and difficulties with mobility. If CPPD is caused by another illness, the seriousness will depend on the underlying condition.
Can calcium pyrophosphate deposition (CPPD) be prevented?
Unlike gout, there is no treatment or diet that can prevent the formation of CPP crystals. If an underlying condition caused an episode of pseudogout (eg, lack of fluid (dehydration) or low magnesium levels), treating this may prevent further attacks.
Like osteoarthritis, the damage from chronic CPP crystal arthritis can be limited by keeping your weight normal and getting a moderate amount of exercise.
Further help & information
Dr Laurence Knott
Dr Laurence Knott
Dr John Cox