RYR1 and congenital myopathy with cores: Mutations in the RYR1 gene have been implicated in a variety of rare congenital myopathies that include, multi-minicore disease (MmD), central core disease (CCD), and to a lesser extent, centronuclear myopathy (CNM), congenital fiber-type disproportion (CFTD), and King Denborough syndrome [11].