Pseudogout is a form of arthritis characterized by deposits of calcium pyrophosphate dihydrate (CPPD) crystals in a joint. Patients experience painful arthritic attacks in their joints, usually in the knee.

Pseudogout, also known as chondrocalcinosis or CPPD disease, is most common in older people. The exact cause of pseudogout and CPPD deposits is unknown. CPPD deposits may be linked to other disorders, such as rheumatoid arthritis. Heredity and joint trauma may also play a role in the development of pseudogout.

Gout and pseudogout have similar symptoms and are often confused with one another. The two main differences are the chemical compositions of crystal deposits and the areas of the body affected. Crystal deposits associated with pseudogout are composed largely of calcium, whereas gout crystals are made of uric acid. Furthermore, pseudogout is most common in the knees, but gout typically affects joints of the toes and feet.

A person with pseudogout may also have gout or another related disease. This often complicates diagnosis. Furthermore, some people may have large deposits of CPPD in certain joints and never experience the painful symptoms of pseudogout. Because of the possibility for overlap, a physician may also consider other causes of joint trouble, even when pseudogout has been diagnosed.

Pseudogout may be treated a number of ways depending upon the painfulness of attack. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen can be taken orally for moderate pain.

Pseudogout, also known as chondrocalcinosis or calcium pyrophosphate dihydrate deposition disease, is a form of arthritis. Attacks occur when calcium pyrophosphate dihydrate (CPPD) crystal deposits that can accumulate in soft tissues and joint spaces are released, causing a severe and painful inflammatory reaction in the affected location.

Pseudogout occurs most frequently in the knees but may also affect the hands, wrists and other jointed areas. Over time, pseudogout can damage the cartilage of a joint, causing bones to painfully rub together. In rare cases, CPPD crystals similar in appearance to those of gout may accumulate in joints, causing them to deteriorate.

Exactly what causes CPPD deposits that lead to pseudogout inflammation is unclear. The formation of crystals may be due to abnormally high levels of calcium or phosphorus in the bloodstream. Phagocytes (cells that kill and remove foreign bacteria) may stimulate pseudogout attacks when they combat disease, although how this may occur is not understood. Other theories suggest that people whose bodies produce too much cartilage (tissue that cushions and connects bones and joints) may have a higher risk of developing pseudogout.

As the name indicates, attacks of pseudogout can resemble gout attacks in many instances. Crystals associated with gout and pseudogout may cause similar inflammation, and the conditions can coexist. However, the two diseases differ significantly in important ways. Pseudogout results from buildups of CPPD deposits for largely unknown reasons. Conversely, gout crystals are caused by the accumulation of uric acid, usually when the body is unable to remove it in urine. Medications or eating habits can contribute to uric acid levels in the body, whereas CPPD buildups are not thought to share this same relation to diet.

Symptoms of pseudogout often mimic those of related conditions, including rheumatoid arthritis and gout, complicating diagnosis. It affects men and women equally and is typically a disease of the elderly. The average age of people with pseudogout is over 70, with almost half of all patients aged 85 or older. It is rarely seen in younger people and almost never in anyone under 30. The correlation between age and prevalence of the disease suggests that the aging process increases susceptibility to pseudogout.

About 3 percent of people in their 60s and up to half of people in their 90s have deposits of CPPD crystals in their joints but may experience no problem unless an insult to a joint releases the deposits, according to the American College of Rheumatology.

Most joints with pseudogout deposits revealed by x-ray do not cause any pain. When painful attacks do occur, however, pseudogout may manifest itself in ways similar to a variety of other disorders, such as:

• Gout. It is difficult to clinically differentiate between gout and pseudogout. Because gout and pseudogout crystals are composed differently, it must be established which crystal type is causing the joint inflammation. Crystal deposits associated with pseudogout are made primarily of calcium, unlike gout crystals, which are made of uric acid. Furthermore, attacks of gout typically occur in joints of the toes and feet, whereas pseudogout typically occurs in the knees.

Awareness of these patterns alone is insufficient in making a distinction between gout and pseudogout; further testing is required. Usually, the only difference is the type of crystal in the joint. Pseudogout crystals extracted in an arthrocentesis are positively birefringent (able to split a ray of light in two) under a polarized light microscope, but gout crystals are negatively birefringent. Trauma, surgery or illness may cause attacks of gout, pseudogout or a combination of the two.

• Osteoarthritis. Many people with pseudogout exhibit degeneration of one or more joints in ways similar to osteoarthritis (deterioration of cartilage in the joints). Calcium pyrophosphate dihydrate (CPPD) crystal deposits, which cause attacks of pseudogout, are often present in osteoarthritic joints. CPPD crystal deposits are thought to play a role in the progression of osteoarthritis in some cases, although the reason for this is uncertain.
  
  
• Rheumatoid arthritis. People with rheumatoid arthritis experience inflammation of multiple joints. Certain symptoms of pseudogout may closely resemble rheumatoid arthritis, such as stiffness, fatigue and persistent restricted range of motion in joints. Furthermore, pseudogout may worsen the damage caused by rheumatoid arthritis if both are present in the same joint.
  
  
• Neuropathic joint disease. Diseases that can cause one or more joints to deteriorate and lose sensation (e.g., diabetes, tabes dorsalis and syringomyelia) may be accompanied by CPPD deposits. The affected joint is known as a Charcot joint. In these instances, the underlying cause of Charcot joint may be strengthened by the presence of a CPPD deposit.

Pseudogout is most common in the elderly. It involves deposits of calcium pyrophosphate dihydrate (CPPD) crystals in joints. However, exactly why these deposits occur is unknown. Diet and the intake of certain calcium-rich substances, such as milk, do not increase the risk of getting pseudogout attacks. However, there are several other factors thought to be associated with the formation of CPPD deposits and pseudogout, including:

• Gout. Often occurs simultaneously with pseudogout. Crystal deposits associated with gout are made from uric acid, as opposed to pseudogout crystals, which are made from calcium. Furthermore, gout often affects the toes and feet, whereas pseudogout is more common in the knees. These two diseases are thought to be connected, although how or why is unclear.
  
  
• Joint trauma. People who have experienced severe joint trauma, including surgery such as a joint replacement (arthroplasty), have higher rates of pseudogout than others who have not. If evidence of CPPD deposits is found, a physician may seek information about a patient’s trauma history.

• Hypercalcemia (excessive calcium in the blood). Causes of hypercalcemia include hypothyroidism (underactive thyroid gland), hyperparathyroidism (overactive parathyroid glands), hemochromatosis (inherited disease marked by excessive storage of iron), hypomagnesia (magnesium insufficiency) or hypophosphatasia (inherited bone disease marked by insufficient phosphate). Other conditions that may increase the risk of pseudogout include acromegaly (gigantism), Wilson's disease (inherited disorder in which copper accumulates in the tissues) and ochronosis (condition marked by blue-black discoloration of tissues).
  
  
• Stress. Stress from medical illness may be a cause of pseudogout.
  
  
• Heredity. Family history of pseudogout increases the risk of developing the condition.

Pseudogout often mimics many other conditions and diseases. Its signs and symptoms are typically consistent with different types of arthritic pain.

The main indicator of a pseudogout attack is usually sharp knee, wrist, shoulder or hip pain, or pain in other major joints. It usually affects only one joint or a few joints at a time. The affected area may be sensitive to touch, swollen or stiff. The pain may last for several days before disappearing and then reappearing in a different joint. Some patients may experience persistent aches or stiffness in joints of the legs and arms between attacks, which are often confused with symptoms of rheumatoid arthritis.

An abnormally high white blood cell count (leukocytosis) may occur in reaction to attacks of pseudogout inflammation. However, some people with crystal deposits in joints never experience any pain or other symptoms at all.

Other minor symptoms might also occur during a pseudogout attack, including:

• Low-grade fever
• Skin discoloration
• Swollen joints

Pseudogout can be difficult to diagnose because it often mimics other medical disorders, including gout. A physician will review the patient’s medical history and typically will perform a physical examination. Additional testing methods are also used to distinguish pseudogout from other painful conditions, such as osteoarthritis. These tests can include:

• Arthrocentesis. A needle is inserted into the affected joint and synovial fluid (fluid that lubricates and protects joints and tendons) is removed for analysis under a microscope. The presence of calcium pyrophosphate dihydrate (CPPD) deposits in the affected joint indicates pseudogout. Pseudogout crystals are positively birefringent (able to split a ray of light in two) under a polarized-light microscope, as compared to gout, where crystals are negatively birefringent. Arthrocentesis is the only testing method that can provide a definitive diagnosis of pseudogout.
  
  
• X-rays. This imaging test may reveal small calcium deposits along joint linings. However, crystal deposits are not detected with x-rays in all cases.
  
  
• Blood tests. Blood testing may show the presence of CPPD deposits in the bloodstream but is often inconclusive. It is most often used along with one or more additional testing methods to rule out other potential causes of joint pain.

There are no known ways to prevent pseudogout. However, there are ways to help minimize the frequency and painfulness of attacks, including:

• Exercising. A sore joint will become weak and more prone to an attack if unused. Regular exercise helps keep muscles that surround joints strong and resilient. Exercise is also an important part of maintaining a healthy weight, which reduces joint stress. Low-impact exercises, such as stretching, swimming and walking, are particularly effective in reducing joint pain.
  
  
• Applying heat and cold. The application of heat (e.g., hot shower) may help relax sore joints and muscles. Similarly, cold (e.g., ice pack) may help reduce pain and swelling.

Treatment is usually effective in stopping acute (sudden or sharp) pain resulting from pseudogout. Treatment methods include:

• Nonsteroidal anti-inflammatory drugs (NSAIDs). These drugs (e.g., ibuprofen) help reduce pain and swelling.
  
  
• Colchicine. This alkaloid medication can also relieve the symptoms promptly during acute attack.
  
  
• Arthrocentesis. The joint area is numbed and a needle inserted to remove fluid containing crystal deposits. This is often performed in conjunction with a corticosteroid injection to reduce swelling and minimize further pain. Short-term oral corticosteroids may also be prescribed to relieve an attack.
  
  
• Joint immobilization. In cases where pain from pseudogout severely inhibits movement, splinting or other immobilization of the inflamed area may help reduce pain for a short period of time. Splinting may be done as part of occupational therapy or physical therapy.
  
  
• Surgery. In severe cases of pseudogout, surgery may be required to remove deposits of calcium pyrophosphate dihydrate (CPPD) from affected joints. However, surgical removal of CPPD deposits will not prevent future CPPD buildup or attacks of pseudogout and is rarely performed.

Current methods of pain treatment cannot prevent damage to joints already affected by CPPD deposits and attacks of pseudogout. Nor are there effective long-term treatments that cure pseudogout or remove crystals permanently. However, daily oral use of certain drugs (e.g., ibuprofen, colchicine) may reduce the frequency of attacks and make them less severe.

In instances where a disease associated with pseudogout (e.g., hypoparathyroidism, hemochromatosis) is present, treatment for the underlying disorder will not reverse CPPD but may reduce or stop the attacks of pseudogout.

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about pseudogout:

1. Do injuries sustained to my joints, such as while playing sports, make me more susceptible to getting pseudogout?
   
   
2. Do I have any other risk factors for pseudogout?
   
   
3. Could pseudogout be the cause of my symptoms? What else could explain my symptoms?
   
   
4. What tests for pseudogout might I need to undergo, and what do they involve?
   
   
5. What do my test results show?
   
   
6. What are my treatment options, and which do you recommend?
   
   
7. What long-term therapeutic approaches do you recommend to minimize pain associated with pseudogout?
   
   
8. Do I need to limit physical activity to reduce the chance of another attack? Are there certain exercises I should perform?
   
   
9. Are members of my family likely to develop pseudogout?
   
   
10. What other conditions or diseases am I at risk for if I have pseudogout?
    
    
11. Should I be tested for conditions similar to pseudogout?