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CPPD Disease — SCE Rheumatology MCQ

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HardCrystal ArthropathyCPPD DiseaseSCE Rheumatology

A 42-year-old with recurrent CPP crystal arthritis has muscle cramps, low potassium, metabolic alkalosis and renal magnesium wasting. Which associated abnormality is most relevant to the crystal disease?

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Correct answer: C — Hypomagnesaemia associated with a renal salt-wasting tubulopathy

The best answer is “Hypomagnesaemia associated with a renal salt-wasting tubulopathy”. Chronic magnesium depletion, including from Gitelman syndrome, predisposes to CPP crystal deposition and is suggested by hypokalaemic metabolic alkalosis with renal magnesium wasting. The alternative biochemical patterns do not explain the stated renal losses or the CPP association.

Reference: EULAR CPPD recommendations: https://ard.bmj.com/content/70/4/571