Tophus
Author:
Mikael Häggström [note 1]
Preparation
A tophus specimen should be sent dry to the pathology department, and not be put in formalin.[notes 1] A touch prep can be done initially, and at least if urate crystals remain suspected, the specimen is submitted in 100% alcohol for microscopy evaluation.
Microscopy evaluation
Evaluation of a fresh tophus can start as a touch prep to look for needle-shaped crystals of urate. On polarized light, these will have negative birefriengence.
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Light microscopy of a touch preparation of a gout tophus, showing needle shaped crystals
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Uric acid crystals in polarized light, showing negative birefringence, with yellow color when aligned parallel to the axis of the red compensator, and blue when aligned perpendicularly to it.[1]
![Uric acid crystals in polarized light, showing negative birefringence, with yellow color when aligned parallel to the axis of the red compensator, and blue when aligned perpendicularly to it.[1]](/index.php?title=Special:Upload&wpDestFile=Uric_acid_crystals_in_polarized_light.png){kind=link}
Notes
- ↑ Formalin dissolves the crystals.
- ↑ For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Patholines:Authorship for details.
Main page
References
- ↑ Bruce M Rothschild. Gout and Pseudogout Workup. Medscape. Updated: Jun 30, 2020
Image sources