An unusual ryanodine receptor 1 (RYR1) phenotype: Mild calf-predominant myopathy.

Our findings expand the spectrum of RYR1-related disorders to include a calf-predominant myopathy with core pathology and autosomal dominant inheritance. Two families had unique and previously unreported RYR1 mutations, while affected persons in the third family carried 2 previously known mutations in the same dominant allele.