Calcium pyrophosphate deposition disease (CPPD) causing pseudogout most commonly deposits crystals in which intra-articular structure, and what is the characteristic appearance on plain radiograph?
- A Synovial membrane — fluffy periarticular calcifications
- B Subchondral bone — dense sclerotic lines paralleling joint surface
- C Fibrocartilage and hyaline cartilage — chondrocalcinosis appearing as linear calcification in joint space ✓
- D Tendon sheaths — punctate calcifications around the joint
Explanation
CPP crystals deposit predominantly in fibrocartilage (menisci of the knee, triangular fibrocartilage complex of the wrist, pubic symphysis) and hyaline cartilage, producing the radiographic finding of chondrocalcinosis — linear or stippled calcification within the cartilage itself, appearing in the mid-substance of the joint space rather than at the joint margins. This is in contrast to hydroxyapatite deposits (calcific tendinitis) which are fluffy periarticular deposits around tendons, and periarticular tophaceous gout which appears differently. Chondrocalcinosis in the knee (meniscal calcification) is a classic CPPD finding but is not specific — it also occurs in hyperparathyroidism, haemochromatosis, hypomagnesaemia, and Wilson's disease.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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