<prompt> The diagnosis of gout is best established by the presence ofSynol uric add crystalsIntracellular uric acid crystalsElevated serum uric acidInvolvement of the first metatarsal phalangeal joint  <response>: Gout Hyperuricemia Gout refers to the disease that occurs in response to the presence of monosodium urate MSU crystals in joints, bones, and soft tissues.Causes of GoutIncreased productionDecreased renal excretionHypoxanthine-guanine phosphoribosyltransferase HGP deficiencyPhosphoribosylpyrophosphate PRPP synthetase overactivityGlucose -6-phosphatase deficiencyMyeloproliferative disorderLymphoproliferative disorderMalignanciesHemolytic disorderPsoriasisObesityEthanol abuseExcessive dietary purine ingestionCytotoxic drugsInherited isolated renal tubular defectRenal failureLead poisoningDiabetic ketoacidosisLactic acidosisHypothyroidismDrugs- thiazides, pyrazinamide, cyclosporineClinical featuresDiagnosisAcute gout -ahritis MP joint of big toe, bursitis olecranon bursa Chronic gout - increase in frequency of acute gouty attacksTophi - collection of solid urate in connective tissues, irregular firm painless nontender nodules on extensor surfaces of finger, hand, and elbow.Polarizing microscopy - identification of monosodium urate crystals Histology - birefringent urate crystals on biopsy Elevated uric acid levels24-hour urinary uric acid excretion Radiology - narrowing of joint space, sclerosis, cysts, osteophytes calcified tophi.Treatment:Acute attack - NSAIDsChronic stage - Allopurinol, Probenecid, benzbromarone Definitive diagnosis of gout requires aspiration of the involved joint and demonstration of intracellular monosodium urate crystals in synol fluid. Under polarized light, these are demonstrated as strongly negative birefringent needle-shaped crystals.Refer: Harrisons Principles of Internal Medicine, 18th edition, pg no: 2836-2839 