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Glycogen storage disease
Transcript of Glycogen storage disease
Diagnosis is important not only for treatment and prognostication but also for genetic counseling and antenatal diagnosis in subsequent pregnancies.
Inborn errors of metabolism are now often referred to as congenital metabolic diseases, or inherited metabolic diseases
IEM is an important cause of acute illness in newborns. In general, metabolic and other inherited disorders can hinder an infant's normal physical and mental development in a variety of ways. Presentation may mimic common neonatal conditions such as sepsis. Parents can pass along the gene for a certain disorder without even knowing that they're carriers. The number of diseases in humans known to be attributable to inherited point defects in metabolism now exceeds 500.1 while the diseases individually are rare.
Major categories of inherited metabolic disorders
- Disorders of carbohydrate metabolism
- Disorder of amino acid metabolism
- Disorders of organic acid metabolism
- Disorders of fatty acid oxidation and mitochondrial metabolism
- Disorders of porphyrin metabolism
- Disorders of purine or pyrimidine metabolism
- Disorders of steroid metabolism
- Disorders of mitochondrial function
- Lysosomal storage disorders
Glycogen Storage Disease
The underlying problem in Glycogen Storage Diseases is the use and storage of glycogen. A person with a glycogen storage disease (GSD) has an absence or deficiency of one of the enzymes responsible for the making or breaking down of glycogen in the body. This is called an enzyme deficiency. The enzyme deficiency causes either abnormal tissue concentrations of glycogen (too much or too little) or incorrectly or abnormally formed glycogen (shaped wrong).
Inborn errors of metabolism
Inborn errors of metabolism
Metabolic disorders (inborn errors
of metabolism) are disorders in which there is a block at some point in the normal metabolic pathway caused by a genetic defect of a specific enzyme, that interfere with the body's use of nutrients to maintain healthy tissues and produce energy. In most of the disorders, problems arise from the accumulation of substances which are toxic or interfere with normal functions
Glycogen Storage Disease
If the enzyme problem is with one of the enzymes involved in glycogen synthesis (production), this causes reduced amounts of normal glycogen to be produced and sometimes abnormal glycogen is being produced. If the enzyme problem is with one of the enzymes involved in glycogen breakdown back into glucose, this can lead to either low levels of glucose in the body (a condition known as hypoglycaemia), or a build-up of glycogen in your muscles and liver
Types of GSD
There are at least 10 different types of GSDs. The types are put into groups based on the enzyme that is missing. The most common forms of GSD are types I (one), III (three) and IV (four). About one in 20,000 people can have a type of GSD.
GSD I, also known as von Gierke disease:
Results from a lack of the enzyme Glucose-6-Phosphatase
GSD III, also known as Cori disease:
Results from a lack of the debrancher enzyme. This causes the body to form glycogen molecules that have an abnormal structure. This abnormal structure also prevents the glycogen from being broken down into free glucose
GSD IV, also known as amylopectinosis:
There is not an increased amount of glycogen in the tissues. Instead, the glycogen that does build up in the tissues has very long outer branches. With this type of GSD, there is lack of the branching enzyme. This abnormal glycogen is thought to stimulate the immune system. The result is a great deal of scarring (cirrhosis) of the liver as well as other organs, such as muscle and heart
GSD in new borns
Glycogen storage disorders are rare. It is estimated that about one in every 20,000 to 40,000 babies born has a glycogen storage disorder. Most, but not all, glycogen storage disorders are inherited in a pattern called autosomal recessive inheritance.
Some disorders affect the liver (types I, IV, VI and IX), some affect the muscles (types V and VII) and some both (type III). Disorders affecting the liver lead to liver enlargement and can be associated with a tendency to low blood sugar. Those affecting the muscles cause muscle weakness and sometimes kidney disease.
Glycogen storage disorders are usually first diagnosed in babies and children. The common features, particularly for type I, include:
- Abnormally slow growth which may be detected by your child's health visitor or GP on routine examination.
- Low blood sugar levels which can cause symptoms such as sweating, tremor, drowsiness, confusion and sometimes convulsions.
- An enlarged liver which a doctor may feel when examining the child's abdomen.
- Noticeably weaker muscles. This can mean that the baby can appear floppy when they are held.
- Problems with bleeding and blood clotting.
- Kidney problems.
GSD symptoms in new borns
The treatment for glycogen storage disorders varies depending on which disorder you have. With most, the treatment aims are to stabilize your blood sugar and energy levels within your body. This is normally achieved by using cornstarch (cornflour as used in thickening gravy) or nutritional supplements such as glucose. A high protein diet is also helpful in some glycogen storage disorders. Some people with glycogen storage disorders who do not respond to nutritional supplements may occasionally need a liver transplant. People with glycogen storage disorders affecting their immune system may need to take regular antibiotics to protect against infection.
GSD treatment options