SNP Shot: Genomic Insights

Glycogen storage disease type 0 (GSD 0) is a disorder where the body struggles to produce glycogen, a complex sugar crucial for storing energy. There are two main forms of GSD 0: muscle GSD 0, characterized by impaired glycogen production in muscles, and liver GSD 0, where glycogen formation in the liver is affected.

Muscle GSD 0 symptoms usually appear in early childhood. Individuals may experience muscle pain, weakness, or fainting spells (syncope) after moderate exertion, such as climbing stairs. These fainting episodes can last for several hours. Some individuals with muscle GSD 0 develop an irregular heartbeat (arrhythmia) called long QT syndrome. Muscle GSD 0 compromises the heart's ability to pump blood effectively in all affected individuals, raising the risk of cardiac arrest and sudden death, especially after physical activity. Tragically, sudden death due to cardiac arrest can occur in childhood or adolescence in those with muscle GSD 0.

Liver GSD 0 typically manifests its signs and symptoms in infancy. Individuals with this form of GSD 0 experience low blood sugar (hypoglycemia) after periods without food (fasting). Symptoms of hypoglycemia become noticeable when infants begin sleeping through the night and stop late-night feedings, displaying extreme tiredness (lethargy), pale skin (pallor), and nausea. Fasting episodes may also lead to increased ketone levels in the blood (ketosis). Ketones are produced when fats are broken down due to the lack of available stored sugars like glycogen. These symptoms of liver GSD 0 usually subside after eating, when glucose levels normalize. The severity of liver GSD 0 varies; it can be mild and undetected for years, or it can result in developmental delays and growth problems.

Inheritance:

GSD 0 is inherited in an autosomal recessive manner. This means that an individual must inherit a mutated copy of the responsible gene from each parent. The parents, who each carry one copy of the mutated gene, are typically asymptomatic carriers.