Patients with inactivating mutations in either STIM1 (e.g. E136X) or Orai1 (e.g. R91W) suffer from congenital myopathy with global muscular hypotonia (Feske, 2009) and Stim1-deficient mice exhibit a severe myopathy associated with perinatal mortality and with myotubes that rapidly fatigue during repeated stimulation (Stiber et al., 2008). Here, STIM1 is linked to congenital myopathy with cores.