Which crystals are characteristic of pseudogout?

Which crystals are characteristic of pseudogout?

• A. Blue positively birefringent rhomboid-shaped crystals
• B. Needle-shaped crystals
• C. Non-birefringent crystals
• D. Pink crystals

Answer: (A)

Pseudogout is defined by calcium pyrophosphate dihydrate crystals that deposit in joints. Under polarized light microscopy, these crystals are rhomboid in shape and show weak positive birefringence, which makes them appear blue when aligned with the slow ray of the compensator. This combination—rhomboid shape and positive birefringence—distinguishes pseudogout from gout, whose crystals are needle-shaped and negatively birefringent (yellow when aligned). Non-birefringent crystals or descriptions like pink crystals do not match CPPD crystals and are not characteristic of pseudogout.

Pseudogout is defined by calcium pyrophosphate dihydrate crystals that deposit in joints. Under polarized light microscopy, these crystals are rhomboid in shape and show weak positive birefringence, which makes them appear blue when aligned with the slow ray of the compensator. This combination—rhomboid shape and positive birefringence—distinguishes pseudogout from gout, whose crystals are needle-shaped and negatively birefringent (yellow when aligned). Non-birefringent crystals or descriptions like pink crystals do not match CPPD crystals and are not characteristic of pseudogout.