Crystal Arthritis Types and Mechanism

Crystal Arthritis

• Two main types of crystal arthritis: sodium urate and calcium pyrophosphate
• Crystals are differentiated under polarized light with a red filter by their shapes and perfringence properties
• Crystals induce arthritis by:
  • Being ingested by neutrophils, which release proinflammatory enzymes from their phagosomes into the joint
  • Activating complement, attracting more neutrophils

Hyperuricaemia

• Defined as serum uric acid level greater than two standard deviations from the mean
• Mean value:
  • Male: 7 mg/dl
  • Female: 6 mg/dl
  • Children: 3-4 mg/dl
• More common in males (10:1 ratio)

Gout and Hyperuricaemia

• Disease of kings, characterized by:
  • Elevated serum uric acid level
  • Recurrent attacks of arthritis
  • Tophi (aggregated sodium urate crystals around joints)
  • Renal disease (glomerular or tubular and interstitial)
  • Urolithiasis

Causes of Hyperuricaemia

• Impaired excretion or increased production
• Decreased excretion:
  • Diseases (chronic renal diseases, hypertension, myxedema, primary parathyroidism)
  • Lead toxicity
  • Certain drugs (thiazide, low-dose aspirin)
  • Increased lactic acid production (alcohol, exercise, and starvation)
• Increased production:
  • Congenital disorders (Lesch-Nyhan syndrome, G6PD deficiency)
  • Myeloproliferative disorders (polycythemia)
  • Lymphoproliferative disorders (leukemia)
  • Carcinoma
  • Psoriasis

Clinical Presentation of Gout

• Four clinical pictures:
  1. Asymptomatic hyperuricaemia
  2. Acute gouty arthritis
  3. Interval gout
  4. Chronic tophaceous gout

Factors Affecting Serum Uric Acid Level

• Age
• Sex (rare before menopause)
• Family history
• Certain diseases (diabetes, ischemic heart disease, hypertension, obesity, and type IV hyperlipidemia)
• Diet (rich in proteins) and alcohol consumption

Suspecting and Diagnosing Gout

• Clinical picture
• Elevated serum uric acid level
• Sure test: joint aspirate and polarized microscopy examination

Classic Gout Attack

• Middle-aged male awakes at night with acute severe pain in the 1st MTP joint after heavy meal and alcohol intake or using diuretics

Management of Gout

• Acute episode:
  • Non-steroidal anti-inflammatory drugs in high dose for 48 hours, then reduced dose for one week
  • Alternative: colchicine or steroids
• Drugs lowering serum uric acid:
  • Allopurinol (300-600 mg, then maintenance dose of 100-300 mg)
  • Inhibits xanthine oxidase enzyme
• Uricosuric drugs: increase urate excretion, may precipitate urate stone formation
• Diet: stop purine-rich diet, red meat, high-calorie diet, cholesterol-rich diet, alcohol, and spinach