This muscle is usually spared until late stages in many genetic muscle diseases (is only affected early in some myofibrillar myopathies, in the Laing distal myopathy and in RYR1-related myopathies (encodes for ryanodine receptor 1 protein) [12, 25–27]), so this finding could be helpful for differential diagnosis. Here, RYR1 is linked to myopathy.