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Crystal arthropathy

Background knowledge 🧠

Definition

  • Crystal arthropathy refers to a group of joint disorders caused by deposition of crystals in and around joints.
  • Most common types are gout (caused by monosodium urate crystals) and pseudogout (caused by calcium pyrophosphate dihydrate crystals).

Epidemiology

  • Gout is more prevalent in males and is associated with lifestyle factors such as diet and alcohol consumption.
  • Pseudogout more commonly affects the elderly.

Pathophysiology

  • Gout: Caused by hyperuricaemia, leading to the deposition of monosodium urate crystals in joints.
  • Pseudogout: Caused by the deposition of calcium pyrophosphate dihydrate crystals, often associated with aging, joint trauma, or metabolic diseases.
  • Crystal deposition triggers an inflammatory response, resulting in acute and painful joint inflammation.

Clinical Features πŸŒ‘️

Clinical Features

  • Gout:
    • Sudden onset of severe joint pain, swelling, and redness, often starting in the big toe (podagra).
    • May progress to involve other joints, with intermittent attacks.
    • Tophi (urate crystal deposits) may form in chronic cases.
  • Pseudogout:
    • Similar presentation to gout but commonly affects larger joints like knees and wrists.
    • Attacks may be less severe than gout.

Investigations πŸ§ͺ

Tests

  • Clinical diagnosis based on symptomatology and joint involvement.
  • Joint aspiration and crystal analysis under polarised light microscopy is definitive.
    • Urate crystals are needle-shaped and negatively birefringent.
    • CPPD crystals are rhomboid-shaped and positively birefringent.
  • Imaging (X-rays, ultrasound) can show typical changes associated with chronic disease.

Management πŸ₯Ό

Management

  • Acute Attack:
    • NSAIDs, corticosteroids, or colchicine for inflammation and pain relief.
  • Long-term Management:
    • Lifestyle modifications for gout: diet changes, reducing alcohol intake, weight loss.
    • Urate-lowering therapy (e.g., allopurinol) for chronic gout.
    • No specific long-term therapy for pseudogout, but underlying metabolic disorders should be managed.

Prognosis

  • Acute attacks can be effectively managed with prompt treatment.
  • Chronic management reduces the frequency and severity of attacks.
  • Potential for joint damage and deformity in chronic, untreated cases.

Prevention

  • Lifestyle modifications, particularly for gout: avoiding high-purine foods and excessive alcohol, maintaining healthy weight.
  • Adequate hydration.
  • Regular monitoring and treatment adherence in patients with known hyperuricaemia.

Key Points

  • Crystal arthropathy often refers to gout or pseudogout and is caused by deposition of crystals in and around joints.
  • Both have similar presentations, with sudden onset of severe joint pain, swelling, and redness.
  • Gout often starts in the big toe (podagra), whereas pseudogout affects larger joints.
  • Joint aspiration and crystal analysis under polarised light microscopy provides a definitive diagnosis.
  • Acute attacks require NSAIDs, corticosteroids, or colchicine with lifestyle modifications and urate-lowering therapyΒ for long-term management.

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