Also known as glycogen synthase deficiency.
The enzyme glycogen synthase is needed for the body to make glycogen. A deficiency results in very low amounts of glycogen stored in the liver. A person between meals can develop very low blood sugar levels, known as hypoglycemia.
Early in infancy children usually have no symptoms. The hypoglycemia typically develops once night feeding stops. Before breakfast children may have drowsiness, look pale, have vomiting, fatigue and sometimes convulsions. If a GP investigates a child lacking energy, hypoglycemia is often discovered through morning urine samples.
Children may become tired more quickly than their peers. There may be muscle cramps from accumulated lactic acid. Children may have a mild growth delay, but in general will develop normally, with normal appearance and liver size.
A history of needing frequent meals or snacks, tiring quickly and hypoglycemia may suggest GSD Type 0. Detailed blood and urine tests may show patterns that are unique to GSD 0 and a liver biopsy will show very little glycogen. DNA testing is now available, the condition being caused by a change in the glycogen synthase-2 (GYS2) gene. It is inherited in an autosomal recessive fashion.
Treatment aims to prevent hypoglycemia by taking snacks every 3-4 hours. Uncooked cornstarch can act as a 'slow release' form of glucose and may prevent hypoglycemia overnight. A diet higher than normal in protein may help with the cramping, tiredness and fatigue.
GSD Type 0 is very rare but the recent availability of better testing may show it to be less rare. The condition affects both males and females and cases have been seen all around the world.
Association for Glycogen Storage Disease (UK) LimitedRegistered Charity No 1132271