Patients with severe gain-of-function CaSR mutations may also have Bartter syndrome type 5, which is characterised by hypokalaemic alkalosis, renal salt wasting and hyperreninaemic hyperaldosteronism (Vargas-Poussou et al. 2002, Watanabe et al. 2002, Kinoshita et al. 2014). The gene discussed is CASR; the disease is Bartter syndrome with hypocalcemia.