Glycogen Synthase Deficiency (GYS2) Sequencing
|Disorder||Glycogen Synthase Deficiency
Glycogen Storage Disease, type 0
|Clinical info||Glycogen synthase deficiency, or glycogen storage disease type 0, is caused by mutations in the GYS2 gene that prevent the synthesis of glycogen in the liver. Symptoms of this condition usually appear in infancy or early childhood, and they include fasting hypoglycemia, ketosis, and low levels of lactate and alanine in blood. Hyperglycemia and hyperlacticacidemia often occur after eating. Some individuals with glycogen synthase deficiency may be relatively asymptomatic with occasional episodes of fasting hypoglycemia, while others may experience recurrent fatigue and vomiting, particularly during periods of fasting or illness. Severe episodes of hypoglycemia may present with pallor, drowsiness, confusion, seizures, and ultimately coma if left untreated. Muscle cramping, exercise intolerance, and minor growth delays may occur, but intelligence is generally not affected. Unlike many storage conditions, glycogen levels are decreased in the liver, so hepatomegaly is typically absent. Most symptoms can be relieved by dietary intervention. Glycogen synthase deficiency is inherited as an autosomal recessive condition and is believed to be significantly underdiagnosed.|
|Indications||Molecular testing is useful to confirm the diagnosis and to identify the disease causing mutation within a family to allow for carrier testing and prenatal diagnosis.|
|Specimen Requirements||5 to 10 ml of peripheral blood collected in an EDTA (lavender top) Vacutainer tube is preferred. The minimal blood needed for reliable DNA isolation is 3 ml.|
|Transport||The specimen should be kept at room temperature and delivered via overnight shipping. FedEx is preferred. If shipment is delayed by one or two days, the specimen should be refrigerated and shipped at room temperature. Do not freeze the specimen. Samples collected on Friday can be safely designated for Monday delivery.|
|Turnaround time||3 weeks|
|Prenatal testing||Prenatal diagnosis is available if the familial mutation is known. Additional fees for cell culture and maternal cell contamination may apply. Maternal cell contamination studies are required for all prenatal molecular tests. Contact the laboratory prior to sending a prenatal specimen.|
Unknown mutation: 81479
|Cost||$1200 for full sequencing (unknown mutation)
$350 for known mutation
Prenatal diagnosis for known mutation is $1000. Please contact the laboratory for more information.
Molecular Diagnostic Lab
The Molecular Diagnostic Lab offers DNA analysis for many genetic disorders via gene sequencing, targeted mutation analysis, MLPA deletion/duplication testing, trinucleotide repeat analysis and next generation sequencing panels.