Recurrent FXYD2 p.Gly41Arg mutation in patients with isolated dominant hypomagnesaemia

*These authors contributed equally to this work. Background. Magnesium (Mg2+) is an essential ion for cell growth, neuroplasticity and muscle contraction. Blood Mg2+ le-vels <0.7 mmol/Lmay cause a heterogeneous clinical phenotype, including muscle cramps and epilepsy and disturbances in K+ and Ca2+ homeostasis. Over the last decade, the genetic origin of several familial forms of hypomagnesaemia has been found. In 2000, mutations in FXYD2, encoding the γ-subunit of the Na+–K+-ATPase, were identified to cause isolated dominant hypomagnesaemia (IDH) in a large Dutch family suffering from hypomagnesaemia, hypocalciuria and chondrocalcinosis. However, no additional patients have been identified since then. Methods. Here, two families with hypomagnesaemia and hypocalciuria were screened for mutations in the FXYD