Homozygous RYR1 mutations have been identified in consanguineous families of different ethnic background with the moderate form (with or without hand involvement) of MmD [23,24]; despite distinct histopathologic appearance, clinical features and findings on muscle imaging were similar to those observed in CCD secondary to heterozygous dominant RYR1 mutations. This evidence concerns the gene RYR1 and multiminicore myopathy.