Background Glycogen Storage Disease (GSD) Type IIIa is a recessively inherited disorder caused by a deficiency in the debranching enzyme amylo-1,6-glucosidase. This deficiency allows for the accumulation of glycogen in the liver, heart and skeletal muscle. Typically patients present in infancy with recurrent hypoglycaemia and hepatomegaly. Standard treatment is a high carbohydrate, moderate to high protein and low fat diet, with regular feeds to help maintain euglycaemia. Conversely the ketogenic diet (KD) consists of a very high fat, low carbohydrate diet with moderate protein intake and has traditionally been used for treatment of epilepsy. It has well noted that ketone bodies can be used as an alternative energy source when carbohydrate intake is low to maintain euglycaemia.
Patient×is a 3 year old male who had neonatal hypoglycaemia and confirmed homozygosity for the GSD Type IIIa gene. Patient×was commenced on the KD at 8 months of age when progression of his GSD resulted in severe cardiomyopathy. The following outlines the transition onto the KD and clinical findings between 8-22 months
Method Standard dietetic treatment was provided from birth to maintain euglycaemia along with placement of a percutaneous endoscopic gastrostomy. Continuous 24 hour feeding was required due to unsuccessful bolus feeding. A modified KD incorporating MCT fat -which was has been noted to further aid ketosis was commenced at 8 months with a ketogenic ratio of 0.5:1 building to 1:1 within 2 weeks. Ketones and blood sugar levels were closely monitored with a threshold of 2.6 mmol/L of glucose and ketones >1 mmol/L before hypoglycaemia intervention was required.
Results Prior to the KD, there was a high glucose infusion rate (GIR) of 9.75 mg glucose/kg/minute. After initiation of the KD, the GIR reduced initially to 5.8 mg glucose/kg/minute, with a gradual increase of MCT fat from 6% to 28% and the GIR further reduced to 2.73 mg glucose/kg/minute. There were no episodes of hypoglycaemia and ketones ranged from 1– 2.9 mmol/L. Echocardiographs showed a significant improvement in cardiac function with a cardiac output reduction of 137 to 39 mmHg.
Discussion The KD was trialled as an alternative treatment. It resulted in the reduced intake of carbohydrate and the subsequent reduction of glycogen build-up within cardiac muscle. Ketones were used as an alternative fuel source and euglycaemia was maintained
Conclusion The KD should be considered as an alternative treatment for GSD Type IIIa where standard intervention is not effective.
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