KCNJ11 encodes an important component of the potassium channel that plays a critical role in regulating the response of beta cells in the pancrease to changes in blood glucose level.  Mutations in this gene can cause inappropriately reduced or elevated insulin secretion.  In a large and extended consanguineous Saudi family, we show for the first time that mutation in KCNJ11 can result not only in congenital hyperinsulinism, but can also lead to vulnerability of skeletal muscles to undergo necrosis in response to strenuous exercise (rhabdomyolysis).  Our report expands the phenotype associated with KCNJ11 mutation in humans. (By Dr Fowzan S Alkuraya, http://jmg.bmj.com/content/early/2014/01/13/jmedgenet-2013-102085 )