Dietary management of Type I glycogen storage disease.

The most commonly recognized type of glycogen storage disease (von Gierke's disease) results from deficient glucose-6-phosphatase activity. This enzyme is the last step in the release of free glucose from the liver into the circulation. Thus, the most prominent and life-threatening complication in the illness is severe and often prolonged hypoglycemia, which occurs after the dietary glucose is normally removed from the circulation. With an optimal dietary intake spaced at 2 1/2- to 3 1/2-hour intervals, the blood glucose can be maintained in the normal range during the daytime, but hypoglycemia may occur during overnight fasting. Recent advances in the understanding of the pathophysiology of the illness have led to the use of frequent high-starch feedings during the day and nocturnal intragastric infusions of liquid formulas containing glucose polymers. The liquid formula is infused through either a nasogastric or a gastrostomy tube continuously at night while the patient sleeps. The success of this treatment not only has improved the survival rate but also has corrected the abnormal blood chemistries and generated a more normal rate of growth and development. Because patients with this disease are reaching adulthood in greater numbers, it is necessary for dietitians caring for adults as well as for children to become familiar with the prescribed methods of treatment.