Browsing Pathways

Glycogenosis, Type IA, also called Von Gierke Disease, is a rare inborn error of metabolism (IEM) and autosomal recessive disorder and caused by a defective glucose-6-phosphatase. Glucose-6-phosphatase catalyzes the conversion of glucose 6-phosphate into D-glucose and conversion of D-glucose to glucose 6-phosphate. Symptoms of the disorder include hypoglycemic seizures, lactic acidosis, hyperuricemia, etc. Treatment with diet management is very effective.

Glycogenosis, Type IC, a sub-category of glycogen storage disease type I, is a rare inborn error of metabolism (IEM) and caused by a defective glucose-6-phosphatase translocase. Glucose-6-phosphate translocase transports glucose 6-phosphate from endoplasmic reticulum (ER) to cell, which glucose 6-phosphate is required for various pathways as the substrate. This disorder damages the ability of converting glycogen into glucose. Symptoms of the disorder include longer sleeping time through night, tiredness and seizures due to low blood sugar. Treatment with diet management is very effective. Currently, only few cases have been reported.

Glycogenosis, Type IB, also called von Gierke disease or GSDI, is a rare inborn error of metabolism (IEM) and autosomal recessive disorder which caused by a defective glucose-6-phosphate translocase. Glucose-6-phosphate translocase transports glucose 6-phosphate from endoplasmic reticulum (ER) to cell, which glucose 6-phosphate is required for various pathways as the substrate. This disorder damages the ability of converting glycogen into glucose. Symptoms of the disorder include longer sleeping time through night, tiredness and seizures due to low blood sugar. Treatment with diet management is very effective.

Triosephosphate isomerase deficiency is a genetic disorder caused by a mutation in the TPI1 gene. The mutation of this gene causes the production of enzymes that are unstable or enzymes that have reduced activity. This means that cells have reduced energy supplies as glycolysis is compromised. This disorder causes anemia, movement problems and muscle weakness. As a result of the lack of red blood cells to carry oxygen through the body, patients may experience fatigue and shortness of breath. Movement problems appear in early infancy, typically before the age of 2 in patients with this disorder. Treatment includes blood transfusions.

Fructose-1,6-bisphosphatase deficiency (FBP1D) is an autosomal recessive inborn error of metabolism (IEM) caused by a mutation in the FBP1 gene which encodes for fructose-1,6-bisphosphatase-1. This enzyme is responsible for catalyzing the conversion of fructose 1,6-bisophosphate into fructose 5-phosphate by removing a phosphate group from it as part of the gluconeogenesis pathway. FBP1D is characterized by hypoglycemia and acidosis after fasting, caused by the impairment of gluconeogenesis. Symptoms can also include hyperventilation. Treatment includes feeding more often with foods enriched with glucose, as well as avoiding foods high in fructose and sucrose, as well as avoiding fasting for longer than overnight. It is estimated that FBP1D affects between 1 in 350,000 and 1 in 900,000 individuals.

Phosphoenolpyruvate Carboxykinase Deficiency 1 (PEPCK1), also called Phosphoenolpyruvate carboxykinase-1 (PCK1) deficiency, Phosphopyruvate carboxylase deficiency, Phosphoenolpyruvate carboxylase deficiency, Phosphoenolpyruvate carboxykinase deficiency, or PEP carboxykinase deficiency, is a rare inborn error of metabolism (IEM) and an autosomal recessive disorder of gluconeogenesis caused by a deficient PEPCK1 enzyme. PEPCK1 catalyzes the conversion of amino acids into sugars, mainly glucose, which is important in preventing hypoglycemia. This disorder is characterized by a large accumulation of lactic acid in the blood. Symptoms of the disorder include hepatomegaly, failure to thrive and liver failure, depending on the severity of the case. Treatment including heavy carbohydrates and fasting is very effective. It is estimated that Phosphoenolpyruvate Carboxykinase Deficiency 1 has only affected 10 individuals around the world according to medical literature.

Glycogen storage disease type 1A (GSD1A), or von Gierke disease, is caused by a defect in the G6PC gene which codes for Glucose-6-phosphatase. Glucose-6-phosphatase hydrolyzes glucose-6-phosphate to glucose and is responsible for the regulation of blood glucose level. A defect in this enzyme results in accumulation of glycogen in affected tissues, like liver and kidney; decreased glucose level; and accumulation of lactate. Glycogen storage disease type 1A causes clinically significant end-organ disease with significant morbidity. Usually it presents in childhood. Symptoms include seizures, irritability, pallor, hypotonia, tremors, loss of consciousness, apnea and hepatomegaly. There is no cure for glycogen storage disease type 1A. Diet therapy can help to prevent hypoglycemia and reduce the symptoms. Liver transplantation may be indicated in cases of hepatic malignancy.

Vitamin A deficiency can be caused by many causes. A defect in the BCMO1 gene which codes for beta,beta-carotene 15,15’-monooxygenase is one of them. Beta,beta-carotene 15,15’-monooxygenase catalyzes the chemical reaction where the two substrates are beta-carotene and O2, whereas its product is retinal. A defect in this enzyme results in decrease of levels of retinal and vitamin A in serum; Signs and symptoms include night blindness, poor adaptation to darkness, dry skin and hair.

Hyperinsulinism-hyperammonemia syndrome (HHS; Glutamate dehydrogenase 1; GLUD1), an inherited condition, is caused by a defect in the GLUD1 gene which codes for mitochondrial glutamate dehydrogenase 1. It is a mitochondrial matrix enzyme, with a key role in the nitrogen and glutamate (Glu) metabolism and the energy homeostasis. An excessive activity of this enzyme results in high insulin and ammonia levels in blood; decrease level of glucose in blood. Symptoms and signs include shakiness, weakness, seizure, rapid pulse and confusion. Maintain normoglycemia is essencial to prevent neurologic damage. Some medications can be used to suppress insulin secretion.

Homocarnosinosis is caused by an inherited defect in serum carnosinase, which converts homocarnosine to GABA (gamma aminobutyric acid). A defect in serum carnosinase causes accumulation of the brain specific dipeptide homocarnosine (Hca), in the CSF and brain. Symptoms include hypotonia, mental retardation, retinitis pigmentosa and spastic diplegia/quadriplegia.