Merck Manual

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Calcium Pyrophosphate (CPP) Arthritis

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

By

Sarah F. Keller

, MD, MA, Cleveland Clinic, Department of Rheumatic and Immunologic Diseases

Medically Reviewed Nov 2022
VIEW PROFESSIONAL VERSION

Calcium pyrophosphate (CPP) arthritis (previously 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 similar to gout 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 CPP crystals in joint fluid.

  • Treatment is with medications to relieve the pain and swelling resulting from the inflammation, although none reduce the CPP crystal deposits in the joints.

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

Causes of CPP Arthritis

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

However, many people with CPP arthritis have none of these conditions. The disorder rarely can be hereditary.

Symptoms of CPP Arthritis

Compared to gout flares, attacks from CPP arthritis vary more in intensity, tend to last longer, and are often more difficult to treat. As in gout, CPP arthritis attacks 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 CPP arthritis rarely develop hard lumps of crystals (tophi).

Diagnosis of CPP Arthritis

  • Microscopic examination of joint fluid

  • Sometimes x-rays or ultrasonography

Doctors suspect CPP arthritis in older people with arthritis, particularly when joints are intermittently swollen, warm, and painful. Doctors confirm the diagnosis by removing a fluid sample from an inflamed joint through a needle (joint aspiration Joint aspiration (arthrocentesis) A doctor can often diagnose a musculoskeletal disorder based on the history and the results of a physical examination. Laboratory tests, imaging tests, or other diagnostic procedures are sometimes... read more Joint aspiration (arthrocentesis) ). CPP 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.

Prognosis for CPP Arthritis

Often, the inflamed joints heal without any residual problems. However, in some people, chronic arthritis and permanent joint damage can occur over time, with some joints so severely destroyed that they can be confused with neurogenic arthropathy Neurogenic Arthropathy Neurogenic arthropathy is caused by progressive joint destruction, often very rapid, that develops because people cannot sense pain, continually injure joints, and thus are not aware of the... read more (Charcot joints).

Unlike gout, chronic CPP arthritis is difficult to treat because there is no therapy that effectively eliminates or reduces the amount of CPP dihydrate crystals. People who have frequent flares, especially younger people, are often evaluated for underlying diseases Causes .

Treatment of CPP Arthritis

  • Drainage of joint fluid and injection of a corticosteroid

  • Medications to relieve pain and swelling resulting from inflammation

  • Physical therapy

Treatment of acute CPP arthritis is similar to that for acute gout Treatment Gout is a disorder in which deposits of uric acid crystals accumulate in the joints because of high blood levels of uric acid (hyperuricemia). The accumulations of crystals cause flares (attacks)... read more Treatment . 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 can be injected into the joint to rapidly reduce the inflammation and pain.

Colchicine (see table ) can be given by mouth in daily low doses (usually 1 or 2 pills) to try to limit the number of flares.

Corticosteroids taken by mouth are effective at treating acute CPP arthritis flares and are particularly useful for some people who should not take NSAIDs or colchicine.

If people cannot tolerate corticosteroids, NSAIDs, or colchicine, drugs that suppress the immune system and inflammation (such as anakinra daily injections) can be effective.

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

Drugs Mentioned In This Article

Generic Name Select Brand Names
NATPARA
ColciGel, Colcrys , GLOPERBA, MITIGARE
Kineret
NOTE: This is the Consumer Version. DOCTORS: VIEW PROFESSIONAL VERSION
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