RYR1 and congenital myopathy with cores: The evidence of cores in muscle histopathology is usually indicational for central core disease (CCD), a congenital myopathy caused by mutations in the gene encoding ryanodine receptor type-1 (RYR1) with muscle weakness defined pathologically by the presence of extensive areas in muscle fibres that are devoid of oxidative enzyme activity (“central cores”) [36,37,38].