CRYSTALS

SUMMARY

1. Intracellular monosodium urate crystals ⇒ gout. These are yellow & termed negatively birefringent.

2. Calcium pyrophosphate crystals ⇒ pseudogout. These are blue & termed positively birefringent.

3. To be certain that the crystals are actually inciting inflammation in the joint, you must see intracellular crystals, which are crystals within the neutrophils, as opposed to just floating freely in the joint space.

4. Crystalline and infectious arthritis can coexist, so it is important to always send studies for both.

5. Calcium hydroxyapatite crystals ⇒ calcific tendonitis.

Reference(s)

Wilkinson, I., Furmedge, D. and Sinharay, R. (2017). Oxford handbook of clinical medicine. Oxford: Oxford University Press. Get it on Amazon.
Feather, A., Randall, D. and Waterhouse, M. (2020). Kumar And Clark’s Clinical Medicine. 10th ed. S.L.: Elsevier Health Sciences. Get it on Amazon.
Hannaman, R. A., Bullock, L., Hatchell, C. A., & Yoffe, M. (2016). Internal medicine review core curriculum, 2017-2018. CO Springs, CO: MedStudy.
Therapeutic Guidelines. Melbourne: Therapeutic Guidelines Limited. https://www.tg.org.au [Accessed 2021].