Acute pseudogout - Measure serum magnesium.

We report a 49-year-old woman with an acute swollen left knee due to acute pseudogout with chondrocalcinosis as a presenting feature of Gitelman syndrome due a novel homozygous mutation of the SLC12A3 gene. This report highlights the under-recognized importance of excluding metabolic disease, including Gitelman syndrome, in younger patients whose sole presenting feature may be chondrocalcinosis with or without pseudogout, as this may impact on management and risk of further episodes. We also suggest that chondrocalcinosis and hypomagnesaemia with or without hypokalaemia are diagnostic of Gitelman syndrome.