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SOURCE

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Source: Fravel MA, Ernst ME. Gout and hyperuricemia. In: DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM, eds. Pharmacotherapy: A Pathophysiologic Approach. 10th ed. New York, NY: McGraw-Hill; 2017. http://accesspharmacy.mhmedical.com/content.aspx?bookid=1861&sectionid=146069254. Accessed May 16, 2017.

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CONDITION SYNONYM

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  • Acute gout.

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DEFINITION

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  • A heterogeneous clinical spectrum of diseases including elevated serum urate concentration (hyperuricemia), recurrent attacks of acute arthritis associated with monosodium urate (MSU) crystals in synovial fluid leukocytes, deposits of monosodium urate crystals (tophi) in tissues in and around joints, interstitial renal disease, and uric acid nephrolithiasis.

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ETIOLOGY

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  • Excess accumulation of uric acid in gout from overproduction or underexcretion of uric acid.

  • Agents that may decrease renal uric acid clearance:

    • Diuretics.

    • Nicotinic acid.

    • Salicylates (<2 g/day)

    • Ethanol.

    • Pyrazinamide.

    • Levodopa.

    • Ethambutol.

    • Cyclosporine.

    • Cytotoxic drugs.

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PATHOPHYSIOLOGY

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  • Uric acid is waste product from purine degradation.

  • Deposition of urate crystals in synovial fluid initiates inflammatory process. Phagocytosis of urate crystals by leukocytes causes lysis of cells and discharge of proteolytic enzymes, resulting in intense joint pain, erythema, warmth, and swelling.

  • Uric acid nephrolithiasis occurs in 10–25% of patients with gout.

    • Risk factors:

      • Excessive urinary excretion of uric acid.

      • Acidic urine.

      • Concentrated urine.

  • In uric acid nephropathy, acute renal failure occurs from blockage of urine flow secondary to massive precipitation of uric acid crystals in collecting ducts and ureters.

  • Tophi may occur in longstanding hyperuricemia and may involve:

    • Great toe.

    • Helix of ear.

    • Olecranon bursae.

    • Achilles tendon.

    • Knees.

    • Wrists.

    • Hands.

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EPIDEMIOLOGY

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  • Affects men 3 times more often than women.

  • Incidence increases with age, peaking at age 30–50 years.

  • Gout more commonly occurs in the older adult.

    • Highest prevalence 12.6% in those 80 years and older.

  • Lowest rates in young women (<45 years), approximately 0.6 cases per 10,000 person-years.

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RISK FACTORS

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  • Elevated serum uric acid concentrations.

  • Male sex.

  • Increasing age.

  • Obesity.

  • Diet and lifestyle:

    • Alcohol, sugary beverages, red meat, and a sedentary lifestyle.

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CLINICAL PRESENTATION

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SIGNS AND SYMPTOMS
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  • Fever, intense pain, erythema, warmth, swelling, and inflammation of involved joints.

  • Attacks are typically monoarticular, most often first metatarsophalangeal joint (podagra), but also insteps, ankles, heels, knees, wrists, fingers, and elbows.

  • Fever and leukocytosis are common.

  • Untreated attacks last from 3–14 days before spontaneous recovery.

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DIAGNOSIS

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MEANS OF CONFIRMATION AND DIAGNOSIS
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  • Presumptive diagnosis based on presence of characteristic signs and symptoms and the response to treatment.

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LABORATORY TESTS
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  • Elevated serum uric acid concentration, but acute gout can occur with normal levels.

  • Leukocytosis.

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IMAGING
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  • X-rays may show asymmetric swelling within joint or subcortical cysts without erosions.

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DIAGNOSTIC PROCEDURES
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  • Definitive diagnosis ...

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