tokens: Other than mutations in sarcomeric genes , which represent the most important cause of HCM in adults , childhood HCM includes a high prevalence of non - sarcomeric causes , including inherited errors of metabolism ( i.e. , glycogen storage diseases , lysosomal storage diseases , and fatty acid oxidation disorders ) , malformation syndromes , neuromuscular diseases , and mitochondrial disease , which globally represent up to 35 % of children with HCM .