Calcification of cartilage due to calcium pyrophosphate dihydrate crystals is best described as which condition?

• A. Gout
• B. Pseudogout (CPPD)
• C. Osteoarthritis
• D. Septic arthritis

Answer: (B)

Calcification of cartilage due to calcium pyrophosphate dihydrate crystals describes pseudogout (CPPD deposition disease). In this condition, CPPD crystals accumulate in joint cartilage and soft tissues, leading to chondrocalcinosis—the characteristic calcification seen in structures like the menisci on imaging. Clinically, it often presents with an acute inflammatory arthritis that can resemble gout, but the crystals are typically rhomboid-shaped and show positive birefringence under polarized light, reflecting the different crystal composition from gout (which involves needle-shaped, negatively birefringent urate crystals). This clarity helps distinguish pseudogout from osteoarthritis, which is degenerative rather than crystal-driven, and from septic arthritis, which is an infection of the joint.