Long-term personalized high-protein, high-fat diet in pediatric patients with glycogen storage disease type IIIa: Evaluation of myopathy, metabolic control, physical activity, growth, and dietary compliance.

Dietary lipid manipulation has recently been proposed for managing glycogen storage disease (GSD) type IIIa. This study aimed to evaluate the myopathic, cardiac, and metabolic status, physical activity, growth, and dietary compliance of a personalized diet high in protein and fat for 24 months. Of 31 patients with type IIIa GSD, 12 met the inclusion criteria. Of these, 10 patients (mean age 11.2 ± 7.4 years) completed the study. Patients were prescribed a personalized high-protein, high-fat diet, comprising 3.0-3.5 g/kg/day of protein and 3.0-4.5 g/kg/day of fat, constituting 18.5%-28% and 70.5%-75.7% of daily energy, respectively. Dietary compliance was ensured and assessed via the regular administration of questionnaires. Our results revealed consistent and significant decreases of 22%, 54%, and 30% in the creatinine kinase, creatine kinase-myocardial band, and lactate dehydrogenase levels, respectively. Echocardiography revealed improvements in the Z-scores of the left ventricular mass and interventricular septum thickness. A significant increase in body muscle mass was observed, and a higher score was achieved using the Daily Activity Questionnaire. Growth monitoring revealed an arrest in the height-SDS at the 6th and 12th months, followed by subsequent improvement at the end of the second year. A gradual and persistent decline in the periods of hypo- and hyperglycemia has been reported. Biotinidase activity decreased, whereas hepatosteatosis increased and then decreased by the end of the study. Implementing a high-protein, high-fat diet and monitoring key parameters in patients with type IIIa GSD can lead to myopathic and cardiac improvements and increased physical activity.