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Pseudogout — SCE Rheumatology MCQ

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ModerateCrystal ArthropathyPseudogoutSCE Rheumatology

A 52-year-old man has a first episode of acute wrist synovitis. Synovial fluid microscopy identifies calcium pyrophosphate crystals, and culture is negative. He has no previously diagnosed metabolic disorder. Which investigation panel is most appropriate to assess for metabolic conditions associated with calcium pyrophosphate deposition disease?

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Correct answer: E — Adjusted calcium and parathyroid hormone, magnesium, phosphate and alkaline phosphatase, ferritin and transferrin saturation, and thyroid function

The correct answer is E. CPPD presenting at a relatively young age should prompt evaluation for associated metabolic disorders. Adjusted calcium and PTH assess for primary hyperparathyroidism; magnesium for hypomagnesaemia or a renal magnesium-wasting disorder; alkaline phosphatase for hypophosphatasia; and ferritin plus transferrin saturation for haemochromatosis. Phosphate and thyroid function are commonly included in a broader metabolic screen, although the association with hypothyroidism is less robust. The other panels investigate metabolic bone turnover, autoimmune connective-tissue disease, spondyloarthritis or acute infection rather than the established CPPD predispositions. Serum urate alone cannot identify these conditions and does not exclude coexisting gout.

Reference: Cowley S, McCarthy G. Diagnosis and Treatment of Calcium Pyrophosphate Deposition (CPPD) Disease: A Review. Open Access Rheumatology. 2023;15:33-41. https://pubmed.ncbi.nlm.nih.gov/36987530/