Crystal Arthropathy

Definition and Epidemiology

• 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).
• 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

• 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.

Diagnosis

• 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

• 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.