Merck Manual

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Calcium Pyrophosphate Arthritis

(Pseudogout; Calcium Pyrophosphate Crystal Deposition Disease; Calcium Pyrophosphate Dihydrate Crystal Deposition Disease)

By

Brian F. Mandell

, MD, PhD, Cleveland Clinic

Last full review/revision Oct 2020| Content last modified Oct 2020
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NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
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Calcium pyrophosphate arthritis (preciously called pseudogout) is a disorder caused by deposits of calcium pyrophosphate dihydrate crystals in the joint cartilage, leading to intermittent attacks of painful joint inflammation or a chronic arthritis similar to rheumatoid arthritis.

  • Crystals accumulate in the fluid and cartilage of the joints, and cause varying degrees of inflammation and tissue damage.

  • The diagnosis is confirmed by finding calcium pyrophosphate crystals in joint fluid.

  • Treatment is with nonsteroidal anti-inflammatory drugs (NSAIDs), colchicine, and sometimes injection of corticosteroids into joints.

Calcium pyrophosphate arthritis usually occurs in older people and affects men and women equally.

Causes

The reason that calcium pyrophosphate dihydrate crystals form in some people is unknown. The crystals often occur in people who have the following:

  • A joint injury (including surgery)

  • Accumulations of an abnormal protein in various organs and tissues (amyloidosis)

  • An abnormally high calcium level in the blood caused by a high level of parathyroid hormone (hyperparathyroidism)

  • An abnormally high iron level in the tissues (hemochromatosis)

  • An abnormally low magnesium level in the blood (hypomagnesemia)

  • A rare disorder that causes an abnormally low alkaline phosphatase level in the blood (hypophosphatasia)

  • Aging

However, most people with calcium pyrophosphate arthritis have none of these conditions. The disorder rarely can be hereditary.

The calcium crystals frequently occur in joints affected by osteoarthritis for unclear reasons.

Symptoms

Symptoms of calcium pyrophosphate arthritis vary widely. Some people have attacks of painful joint inflammation (arthritis) similar to gout flares, usually in the knees, wrists, or other relatively large joints. Other people have lingering, chronic pain and stiffness in joints of the arms and legs, which may be similar to rheumatoid arthritis or osteoarthritis.

Sudden painful (acute) attacks are usually less severe than those of gout, but, as in gout, attacks in calcium pyrophosphate arthritis can cause fever. Some people have no pain between attacks, and some have no pain at any time, despite large deposits of crystals.

Unlike in gout, where collections of crystals often occur in tissues near joints, people with calcium pyrophosphate arthritis rarely develop hard lumps of crystals (tophi).

Diagnosis

  • Microscopic examination of joint fluid

  • Sometimes x-rays or ultrasonography

Doctors suspect the diagnosis of calcium pyrophosphate arthritis in older people with arthritis, particularly when joints are swollen, warm, and painful. Doctors confirm the diagnosis by removing a fluid sample from an inflamed joint through a needle (joint aspiration). Calcium pyrophosphate dihydrate crystals are found in the joint fluid. They can be distinguished from uric acid crystals (which cause gout) using a special microscope with polarized light.

X-rays are done when doctors cannot obtain fluid from the joint. Seeing masses of crystals in a joint's cartilage suggests the diagnosis. Ultrasonography of the joint may show crystals in joint cartilage and strongly suggests the diagnosis of calcium pyrophosphate arthritis.

Prognosis

Often, the inflamed joints heal without any residual problems. However, in some people, chronic arthritis and permanent joint damage can occur, with some joints so severely destroyed that they can be confused with neurogenic arthropathy (Charcot joints).

Treatment

  • Drainage of joint fluid and injection of a corticosteroid

  • Nonsteroidal anti-inflammatory drugs

  • Colchicine to help prevent attacks

  • Physical therapy

Usually, treatment can stop acute attacks and prevent new attacks but cannot reverse changes in already damaged joints. Excess joint fluid can be drained and a corticosteroid suspension can be injected into the joint to rapidly reduce the inflammation and pain.

Drugs taken by mouth help treat calcium pyrophosphate arthritis. Most often, nonsteroidal anti-inflammatory drugs (NSAIDs) are used to promptly stop the pain and inflammation of acute attacks.

Colchicine (see Table: Drugs Used to Treat Gout) can be given by mouth in daily low doses (usually 1 or 2 pills) to limit the number of attacks.

Unlike for gout, no specific effective long-term treatment of calcium pyrophosphate arthritis is available. However, physical therapy (such as muscle-strengthening and range-of-motion exercises) may be helpful to maintain joint function.

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
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