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CPPD associated with hyperparathyroidism — SCE Rheumatology MCQ

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HardCrystal arthropathiesCPPD associated with hyperparathyroidismSCE Rheumatology

A 73-year-old woman has acute knee swelling. Radiograph shows chondrocalcinosis and aspiration reveals rhomboid weakly positively birefringent crystals; Gram stain is negative. Calcium is 2.82 mmol/L and PTH is elevated. What is the most appropriate additional investigation?

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Correct answer: B — Assess for primary hyperparathyroidism

CPPD is confirmed by calcium pyrophosphate crystals and chondrocalcinosis; metabolic associations include hyperparathyroidism, haemochromatosis and hypomagnesaemia. Elevated calcium and PTH specifically require assessment for primary hyperparathyroidism. RA and axial SpA tests would not explain the crystal finding.

Reference: BSR rheumatology curriculum; EULAR CPPD recommendations