RYR1 and congenital myopathy with cores: Mutations in the ryanodine receptor 1 (RYR1) gene lead to a wide spectrum of congenital myopathies such as central core disease (CCD), multi‐minicore disease (MmD), centronuclear myopathy (CNM), and congenital fibre type disproportion (CFTD), with an overall estimated prevalence of 1 in 90 000.1, 2, 3