Glycogen Storage Disease Type 1a (glucose-6-phosphatase deficiency, von Gierkes disease,) is a rare genetic disorder caused by a mutation in the glucose-6-phosphatase gene and results in the absence of a functional glucose-6-phosphatase enzyme (G6Pase). The absence of G6Pase activity in liver cells leads to the inability to convert glycogen to glucose leading to a deficiency in normal metabolic function and hypoglycemia (low blood sugar). Because of the missing /impaired enzyme, the body cannot create glucose from glycogen and therefore it is difficult to maintain normal blood sugar levels between meals without constant feeding. Glucose is the essential energy source for every cell in the body. Dangerous levels of by-products such as lactates, uric acids and triglycerides in combination with low blood sugar can lead to numerous complications in GSD1a including impaired breathing, seizures, coma and death if a very strict dietary regimen is not followed.
Children with this disease appear normal at birth, however, the child will begin to exhibit symptoms such as low blood sugar, an enlarged liver, failure to thrive, developmental delay, elevated lactate and uric acid levels in the blood and urine, and seizures. Because of GSD1a's rarity, these symptoms are often not fully recognized and can lead to misdiagnosis. This will eventually lead to a crisis situation within the first three to four months of life. It is not known how many children die without ever having been properly diagnosed. After GSD1a is identified, the only way to minimize symptoms is to closely monitor blood sugar levels and to adjust diet accordingly. Currently there is no cure for GSD1a.
The management of GSD1a is lifelong. GSD1a not only affects the child, but also deeply affects the parents and family of the child born with this disease. Diet is the cornerstone of treatment and many types of foods are restricted, severely limiting dietary options. GSD1 children should minimize foods containing sucrose (table sugar,) fructose (sugar found in fruits,) and lactose and galactose (sugars found in milk products) because these sugars end up as glycogen trapped in the liver. They also must be fed every one to four hours in order to maintain blood glucose at an appropriate level. This can often be very difficult for young children to tolerate and missing a meal or a feeding time can have catastrophic effects. As a result, most have a gastric or naso-gastric tube inserted to maintain nutrient intake. During infancy, the tube is critical for frequent feeding during the day and for using a continuous feeding pump at night. This alternative route of ingestion also helps during times of normal childhood illnesses when hypoglycemia and acidosis can occur more often. A consequence of having to eat so frequently is that GSD1a children often have problems ingesting food by mouth. They must undergo intensive therapy to relearn sucking, swallowing and even speech patterns.