External ear tumors - benign / nonneoplastic


Topic Completed: 1 October 2013

Minor changes: 14 December 2020

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PubMed Search: Ear gout

Related Topics: Gout and gouty arthritis

Nat Pernick, M.D.
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Cite this page: Pernick N. Gout. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/eargout.html. Accessed December 8th, 2021.
Definition / general
  • Primary gout (90%): idiopathic (85%) due to overproduction of uric acid or known enzyme defects (5%, partial hypoxanthine guanine phosphoribosyl transferase deficiency [HGPRT]); may have normal excretion
  • Secondary gout (10%): increased nucleic acid turnover due to leukemia / lymphoma, chronic renal disease, HGPRT deficiency
Xray description
  • No calcifications
  • Elevated urinary uric acid, leukocytosis, increased erythrocyte sedimentation rate
  • Gouty tophi (depositions of sodium urate) commonly deposit in helix of ear as painful, skin covered, firm nodules
Microscopic (histologic) description
  • Tophi are composed of needle shaped aggregates of urate crystals with surrounding foreign body giant cell reaction
  • Urate crystals dissolve with routine processing, so fix a smear of crystals in absolute alcohol or nonaqueous fixation
  • Under polarized light microscopy, they have a needle-like morphology and strong negative birefringence (J Int Adv Otol 2016;12:216)
Microscopic (histologic) images

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Needle shaped crystals

Differential diagnosis
  • Pseudogout: rhomboid or needle shaped, weak positive birefringence with polarized light, radiographic calcifications
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