We suggest that mutations in the MYH7 gene affecting the C-terminal domain of beta-myosin heavy chain should also be considered as a possible cause in cases of early-onset myopathy with "dropped head" syndrome.
Muscle imaging findings in patients with axial involvement provide significant clues permitting the distinction between MYH7-related myopathies and other axial myopathies such as those related to SEPN1 and LMNA genes.Muscle Nerve 58: 224-234, 2018.
This study expands our clinical and molecular knowledge of MYH7 rod mutations causing skeletal myopathies, and underscores the importance of discussing disease penetrance during genetic counseling.
Furthermore, the proband's childhood-onset distal leg weakness and sister's cardiomyopathy suggest that MYH7p.Arg1820Gln likely affects function, favoring a digenic etiology of the myopathy.
We suggest that this overlapping presentation confirm the phenotypic variability of MYH7myopathy and may be helpful to improve the genotype phenotype correlation.
Cardiac involvement may be present in MYH7-myopathy and may be progressive between the generations, ranging from relaxation abnormality to noncompaction, ventricular arrhythmias, and dilated cardiomyopathy.
These findings suggest MYH7 mutations as another cause of a myopathy with multiple cores, in particular if associated with dominant inheritance and cardiac involvement.
Myosinopathies or myosin storage myopathies also commence in childhood, but show a much more protracted course owing to mutations in the myosin heavy chain gene MYH7.
More than 200 mutations in the beta-myosin gene (MYH7) that cause clinically distinct cardiac and/or skeletal myopathies have been reported, but to date, no comprehensive statistical analysis of these mutations has been performed.
The MYH7 tail domain mutation results in an inclusion body myopathy with an apparent absence of hypertrophic cardiomyopathy usually associated with mutations of this gene.