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Acute CPP crystal arthritis — SCE Geriatric Medicine MCQ

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HardMusculoskeletal medicineAcute CPP crystal arthritisSCE Geriatric Medicine

An 89-year-old woman with severe frailty and diabetes is admitted with a painful swollen wrist. Temperature is 37.9°C, CRP is 112 mg/L and WCC is 15 ×10⁹/L. X-ray shows chondrocalcinosis; synovial fluid microscopy shows positively birefringent rhomboid crystals and Gram stain is negative. What is the most likely diagnosis?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: C — Acute calcium pyrophosphate crystal arthritis

Positively birefringent rhomboid crystals with chondrocalcinosis support acute CPP crystal arthritis. However, crystals do not fully exclude coexisting septic arthritis, so cultures and clinical monitoring remain important. Osteoarthritis flare would not usually produce this inflammatory picture. The pearl is that pseudogout commonly affects older adults and can mimic infection or delirium precipitants.

Reference: BSR crystal arthritis guidance; NICE CKS CPPD