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Pseudogout (CPPD) — RACP Adult Medicine MCQ

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EasyRheumatologyPseudogout (CPPD)RACP Adult Medicine

A 72-year-old woman presents with acute knee swelling. She has known osteoarthritis. X-ray shows chondrocalcinosis of the menisci. Joint aspirate shows positively birefringent rhomboid-shaped crystals. What is the most likely diagnosis?

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Correct answer: E — Calcium pyrophosphate deposition disease

Acute arthritis with chondrocalcinosis on X-ray and positively birefringent rhomboid crystals on polarised microscopy is diagnostic of CPPD (pseudogout). Large joint involvement (knee, wrist) is more common than small joints. Secondary causes (haemochromatosis, hyperparathyroidism, hypomagnesaemia) should be screened for if aged <55.

Reference: eTG Rheumatology – 2024 – Crystal Arthropathy