Does chronic congestive heart failure elicit adaptations of endurance exercise in diaphragmatic muscle?
In the diaphragm in heart failure, there is a shift from fast to slow myosin heavy chain isoforms with an increase in oxidative capacity and a decrease in glycolytic capacity. These diaphragmatic muscle changes are consistent with those elicited by endurance training of the limb muscles in normal subjects.
The only three previously reported families with defects in ELAC2 gene exhibited infantile hypertrophic cardiomyopathy and complex I deficiency. In contrast, our patients exhibited intellectual disability as the main feature with minimal cardiac involvement. Therefore our findings expand the phenotypic spectrum of ELAC2- associated disorders illustrating clinical heterogeneity of mutations in this gene. In addition, ELAC2 mutations should be considered when evaluating patient with mainly intellectual disability phenotypes.