Gout/Pseudogout

Basics

Description

  • Gout: Uric acid deposition into tissues, affecting mainly middle-aged men and postmenopausal women:
    • Most common crystalline diseases
    • 4 phases:
      • Asymptomatic hyperuricemia (serum urate >7 mg/dL)
      • Acute gout
      • Intercritical gout: Quiet intervening periods
      • Tophaceous gout (up to 45% of cases)
    • Risk factors:
      • Age >40
      • Male/female ratio 2:1–6:1 <65 yr old; 1:1 ≥65 yr old
      • Hypertension
      • Use of loop or thiazide diuretics
      • High intake of alcohol, meat, seafood, and fructose-sweetened beverages
      • Obesity
    • Urologic deposition of uric acid calculi may cause renal dysfunction
    • Associated with avascular necrosis and deforming arthritis
    • Most frequent in previously damaged joints or tissues:
      • Synovium
      • Subchondral bone
      • Bursae (olecranon, infrapatellar, prepatellar)
      • Achilles tendon
      • Extensor surface of the forearms, toes, fingers, ear
      • Rarely CNS or cardiac (valves)
  • Pseudogout: A disorder caused by calcium pyrophosphate crystal deposition:
    • Most common cause of acute monoarthritis >60 yr of age
    • Risk factors:
      • Hypercalcemia (eg, hyperparathyroidism, familial)
      • Hemochromatosis; hemosiderosis
      • Hypothyroidism and hyperthyroidism
      • Hypophosphatemia, hypomagnesemia
      • Amyloidosis
      • Gout

Etiology

  • Deposition of monosodium urate crystals in tissues from supersaturated extracellular fluid owing to:
    • Underexcretion (most commonly) or excessive production of uric acid
    • Any rapid change in uric acid levels:
      • Initiation or cessation of diuretics
      • Alcohol, salicylates, niacin
      • Cyclosporine
      • Lead acetate poisoning
      • Uricosurics or allopurinol
  • Pseudogout occurs secondary to excess synovial accumulation of calcium pyrophosphate crystals
  • Precipitants for both gout and pseudogout include minor trauma and acute illnesses:
    • Surgery, ischemic heart disease

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