Pseudogout is an inflammation of joints caused by the deposition of calcium pyrophosphate crystals in articular and periarticular tissues. Calcium pyrophosphate crystals are deposited in cartilage (chondrocalcinosis). Pseudogout is a clinical term for an acute inflammatory process in one or more joints mimicking a gout attack. Pseudogout is therefore just one of the clinical presentations for calcium pyrophosphate dihydrate crystal deposition disease.¹ This process may be:

• Asymptomatic.
• Associated with degenerative changes within the joint.
• A cause of acute arthritis: caused by crystals entering the synovial fluid, and resembles acute gout.²

Epidemiology

• Calcium pyrophosphate crystal deposition is common in the elderly.
• Most cases of chondrocalcinosis are non-familial but there is evidence for genetic factors with many multi-case families with chondrocalcinosis reported.³

May be precipitated by:

• Dehydration
• Intercurrent illness
• Hyperparathyroidism
• Long-term use of steroids
• Hypothyroidism
• Any cause of arthritis
• Haemochromatosis
• Wilson's disease
• Acromegaly
• Dialysis
• Surgery or trauma

Presentation

• Often asymptomatic, with only radiographic changes of chondrocalcinosis.
• Calcium pyrophosphate crystal deposition may cause an acute or chronic arthritis.
• Acute pseudogout:
  • Causes an acute monoarticular or oligoarticular arthritis. It most often affects the knees, but often also wrists, shoulders, ankles, hands and feet. Almost any joint may be affected.
  • Presentation is similar (but usually milder) to acute gout, with acute joint pain and swelling.
  • Affected joints are acutely inflamed with swelling, effusion, warmth, tenderness and pain on movement. Attacks may be associated with fever and raised white cell count.
• Chronic calcinosis:
  • Destructive changes like osteoarthritis (but more severe). May progress to cause a destructive arthropathy producing a neuropathic joint.
  • Most often affects knees, wrists, shoulders and hips.

Differential diagnosis

• Acute gout
• Septic arthritis
• Osteoarthritis
• Rheumatoid arthritis

Investigations

• Joint X-rays: linear opacification of articular cartilage - chondrocalcinosis.
• Ultrasound may also be a useful diagnostic tool.⁴
• Aspiration of the joint fluid: raised white cell count which is predominantly neutrophils. Glucose levels usually are normal. Intracellular and extracellular weakly positive birefringent crystals (intracellular crystals are pathognomonic for acute pseudogout). The joint fluid often looks purulent and septic arthritis must be excluded.
• Exclusion of other causes of acute arthritis.
• Evaluation of possible underlying cause as listed above.

Management

Treatment is symptomatic as well as any specific treatment for an identified underlying cause:

• Aspiration of the joint helps to reduce pain
• Non-steroidal anti-inflammatory drugs (NSAIDs)
• Intra-articular steroid injections
• Systemic steroids
• Colchicine is an alternative if NSAIDs or steroids are contra-indicated.⁵

Prognosis⁵

• Acute attacks usually resolve within 10 days.
• Some patients develop progressive joint damage with functional limitation.
• Prognosis will also be dependent on any underlying cause.

Document references

1. Bencardino JT, Hassankhani A; Calcium pyrophosphate dihydrate crystal deposition disease. Semin Musculoskelet Radiol. 2003 Sep;7(3):175-85. [abstract]
2. Wright GD, Doherty M; Calcium pyrophosphate crystal deposition is not always 'wear and tear' or aging. Ann Rheum Dis. 1997 Oct;56(10):586-8.
3. Timms AE, Zhang Y, Russell RG, et al; Genetic studies of disorders of calcium crystal deposition. Rheumatology (Oxford). 2002 Jul;41(7):725-9.
4. Frediani B, Filippou G, Falsetti P, et al; Diagnosis of calcium pyrophosphate dihydrate crystal deposition disease: ultrasonographic criteria proposed. Ann Rheum Dis. 2005 Apr;64(4):638-40. [abstract]
5. Kaplan J; Gout and Pseudogout, eMedicine, Aug 2009.

Acknowledgements