Von Gierke disease is inherited in an autosomal recessive modality. This means two copies of the abnormal gene must be inherited in order for the disease to develop.
Von Gierke's disease is a type I glycogen storage disease.
This is the enzyme that is essential for the final step of glycogenolysis. If deficient, the patient is unable to mobilize glucose stores via glycogen breakdown.
Without the glucose 6 phosphatase enzyme participating in glycogen breakdown, glycogen stores are unable to be mobilized and accumulate in the liver. It is important to note that patients can make glycogen but cannot break it down.
Hepatomegaly, or an enlarged liver, occurs due to the abundance of glycogen accumulating in the liver.
Glycogen is also stored in the kidneys, thus it also accumulates in the kidney, much like it does in the liver.
Patients lack the ability to maintain blood sugar, because when blood sugar levels are low, glycogen cannot be effectively broken down to glucose in the liver.
Because there is a deficiency of glucose-6-phosphatase, glucose-6-phosphate molecules are shunted into other metabolic pathways. These glucose-6-phosphate molecules are converted into triglycerides, which are exported for storage in adipose tissue as fat.
In Von Gierke disease, increased uric acid accumulates because of numerous reasons. A concurrent lactic acidosis in this disorder leads to decreased urinary excretion of uric acid. Additionally, because glucose-6-phosphatase is deficient, glucose-6-phosphate is shunted through the pentose phosphate pathway to create uric acid.
Lactate increases as the body is forced to utilize alternative means for fuel when blood glucose levels are insufficient.
Patients with Von Gierke disease have a characteristic rounded "doll-like facies" due to fat deposition.
Because patients are hypoglycemic, and cannot participate in glycogenolysis, they must continuously ingest oral glucose. Cornstarch is another dietary option, as it provides gradually digested glucose, and decreases the necessity for constant feeds.
Fructose and galactose should be avoided in Von Gierke patients, as these sugars must first be converted to glucose-6-phosphate before they can be utilized in the body.
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