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Pseudogout (Calcium Pyrophosphate Dihydrate Crystal Deposition Disease)

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Overview

Also known as calcium pyrophosphate deposition disease, pseudogout describes inflammation of joints caused by the deposition of calcium pyrophosphate crystals in articular and periarticular joints. It is another type of crystal arthropathy.

Epidemiology

  • More common in older people (>60 years)
  • More common in men (ratio of 1.5:1)

Risk Factors

Presentation

Pseudogout typically presents acutely (over hours) or sometimes overnight with redness and swelling in a joint. Features include:

  • Pain, redness, and swelling of the knee, wrist, and shoulders
  • It may present as a sudden worsening of osteoarthritis (OA) or features of OA occurring in less typical joints (e.g. OA does not tend to affect the shoulders)

Signs on examination

  • Red and swollen joints
  • Joint effusion and fluctuance

Differential Diagnoses

Gout

  • Gout and pseudogout may present identically
  • Gout tends to attack smaller joints of the feet, such as the first metatarsophalangeal joint
  • Joint aspiration and analysis help differentiate gout and pseudogout

Septic arthritis

  • This may present identically to pseudogout
  • Septic arthritis should be considered in those with features of infection or systemic upset (with or without fever), or those who do not improve with treatment
  • If suspected, refer the patient for emergency joint aspiration and culture
  • There may be risk factors for septic arthritis including prior joint replacement, pre-existing joint damage, a recent intra-articular injection, intravenous drug use, or immunosuppression 

Osteoarthritis (OA)

  • OA tends to affect large, weight-bearing joints (such as the hip or knee), the cervical and lumbar spine, the base of the 1st metatarsophalangeal joint, the first carpometacarpal, the proximal, and the distal interphalangeal joints
  • Involvement of less typical joints (such as the shoulder) may suggest pseudogout
  • Sudden worsening of OA may suggest pseudogout

Polymyalgia rheumatica

  • Patients have proximal muscle (i.e. shoulders and hips) stiffness that is prolonged in the morning, worse with rest, and relieved with exertion
  • There may be associated fever, weight loss, and malaise
  • There is generally very little/no synovitis

Investigations

  • Arthrocentesis with synovial fluid analysis:
    • Positively birefringent rhomboid-shaped crystals under polarised light are diagnostic
  • X-ray of affected joints:
    • May show linear calcifications of the meniscus and articular cartilage
  • Serum calcium:
    • To screen for hyperparathyroidism
  • Iron studies:
    • To screen for haemochromatosis
  • Serum magnesium:
    • To screen for hypomagnesaemia

Management

Management may involve:

  • NSAIDs (unless contraindicated) + paracetamol
    • Consider adding PPI
  • Colchicine (if NSAIDs contraindicated) + paracetamol
  • Intra-articular corticosteroids

Prognosis

  • Acute attacks usually resolve in 10 days
  • Some acute attacks may last weeks or months
  • Some patients develop progressive joint damage with functional limitation
  • Prognosis depends on the underlying cause

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