Tophus: Difference between revisions

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==Preparation==
==Preparation==
A tophus specimen should be sent '''dry''' to the pathology department, and '''not''' be put in formalin.<ref group=notes>Formalin dissolves the crystals.</ref> 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.
A tophus specimen should be sent '''dry''' to the pathology department, and '''not''' be put in formalin.<ref group=note name=dissolves>Formalin dissolves the crystals.</ref>
 
==Gross processing==
[[File:Gross pathology of tophus.jpg|thumb|A large tophus.]]
Preferably make a touch prep for polarized light microscopy. At least if urate crystals are not initially detected, take sections to be put in 100% alcohol and tell the histology lab to prepare it as per gout protocol.<ref group=note name=dissolves/> With characteristic crystals on a touch prep, sections may possibly be submitted in formalin.<ref group=note name=dissolves/>


==Microscopy evaluation==
==Microscopy evaluation==
<gallery mode=packed>
On a touch prep, look for needle-shaped crystals of urate. On polarized light, these will have negative birefriengence.
File:Uric acid crystals in polarized light.png|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.<ref>{{cite web|url=https://emedicine.medscape.com/article/329958-workup|title=Gout and Pseudogout Workup|author=Bruce M Rothschild|website=Medscape}} Updated: Jun 30, 2020</ref>
<gallery mode=packed heights=180>
File:Light microscopy of a touch preparation of a gout tophus, showing urate crystals.jpg|thumb|Light microscopy of a touch preparation of a gout tophus, showing needle-shaped crystals
File:Birefringence microscopy of gout, annotated.jpg|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.<ref>{{cite web|url=https://emedicine.medscape.com/article/329958-workup|title=Gout and Pseudogout Workup|author=Bruce M Rothschild|website=Medscape}} Updated: Jun 30, 2020</ref>
File:Birefringence microscopy of pseudogout, annotated.jpg|In contrast, '''pseudogout''', also called calcium pyrophosphate dihydrate (CPPD) crystal deposition disease) displays rhombus-shaped or parallelogram-shaped crystals with negative birefringence.
File:Calcium pyrophosphate dihydrate crystals without and with condenser.jpg|To look for crystals in a regular light microscope, look without '''condenser''' (right image) if possible, wherein crystal outlines are more clear than with condenser (left image). CPPD crystals are depicted.
</gallery>
</gallery>
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Latest revision as of 16:49, 19 June 2022

Author: Mikael Häggström [note 1]

Preparation

A tophus specimen should be sent dry to the pathology department, and not be put in formalin.[note 2]

Gross processing

A large tophus.

Preferably make a touch prep for polarized light microscopy. At least if urate crystals are not initially detected, take sections to be put in 100% alcohol and tell the histology lab to prepare it as per gout protocol.[note 2] With characteristic crystals on a touch prep, sections may possibly be submitted in formalin.[note 2]

Microscopy evaluation

On a touch prep, look for needle-shaped crystals of urate. On polarized light, these will have negative birefriengence.

  • Light microscopy of a touch preparation of a gout tophus, showing needle-shaped crystals
    Light microscopy of a touch preparation of a gout tophus, showing needle-shaped crystals
  • 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]
  • In contrast, pseudogout, also called calcium pyrophosphate dihydrate (CPPD) crystal deposition disease) displays rhombus-shaped or parallelogram-shaped crystals with negative birefringence.
    In contrast, pseudogout, also called calcium pyrophosphate dihydrate (CPPD) crystal deposition disease) displays rhombus-shaped or parallelogram-shaped crystals with negative birefringence.
  • To look for crystals in a regular light microscope, look without condenser (right image) if possible, wherein crystal outlines are more clear than with condenser (left image). CPPD crystals are depicted.
    To look for crystals in a regular light microscope, look without condenser (right image) if possible, wherein crystal outlines are more clear than with condenser (left image). CPPD crystals are depicted.

Notes

  1. ↑ 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.
  2. ↑ 2.0 2.1 2.2 Formalin dissolves the crystals.

Main page

References

  1. ↑ Bruce M Rothschild. Gout and Pseudogout Workup. Medscape. Updated: Jun 30, 2020

Image sources


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