Different types of GSD

There are different types of GSD and most of them can have very different symptoms, you can find information about the variants below.

Glycogen storage disease

Glucuse is a major source of energy for the body, It is stored in the form of glycocogn in both the liver and muscles and is when needed released in the body with the help of enzymes. The glycogen storage diseases or otherwise known as GSD are a group of inherited metabolic disorders, in common patients with the disease have a defect in any of one of several enzymes needed for the synthesis or breakdown of glycogen. The hepatic (liver) GSDs, are present as fasting intolerance (hypoglycemia), and those with neuromuscular disease and weakness. Some of the GSDs can have both manifestations. There is a wide range of severity, from fatal in infancy if untreated to mild disorders with normal few symptoms and good long-term prognosis. the SAGSD represents only liver types of GSD types 0, I, III, IV, VI, and IX.
 
Click on the button below to read a publication written for the Swedish national board of health and welfare by the SAGSD and Karolinska university hospital.

What it's like to live with GSD

Below you can read some of our members’ stories about what it’s like to live with GSD both as a parent and as a child. To gain an insight into what it is like, we recommend that you read at least one of these articles.

Types of GSD

Below you can read a short description about the different types of GSD. There are around 16 types of GSD plus sub-variants, making about 25 in total, and new types & variants are still being discovered. Additionally you can read official medical studies on the said version of GSD by clicking the “Read Article” button.

Type 0

Type 0 GSD is caused by a deficiency in the enzyme named glycogen synthase. This enzyme is needed for the body to make glycogen. When a person has glycogen synthase deficiency the amount of glycogen that the body can store in the liver is very low. Low amounts of glycogen in the liver mean that when a person is not eating (fasting) their blood sugar levels can get very low (hypoglycemia). In patients with Type 0 Glycogen Storage Disease, the symptom of fasting hypoglycemia typically develops when a baby no longer gets fed during the night (late infancy). There are liver and muscle types of GSD 0.

Type I - von Gierke’s disease

GSD 1 is a rare autosomal recessive disease, there are two types GSD 1a and GSDb. Patients having the disease are not able to release glucose from the liver. Their blood sugar level will become low if the fasting is prolonged. In early childhood they become unwell with sweating, irritability, poor growth, and muscle weakness. An enlargement of the liver will occur due to excessive accumulation of glycogen since it cannot be broken down normally. In addition to these problems, and especially in patients with GSD Ib can develop frequent mouth ulcers and are at increased risk of infection. Treatment of GSD consists of frequent meals, continuous glucose infusion, and in older children and adults uncooked cornstarch is consumed after a meal to stabilize the blood sugar.

Type III - Cori discease & Forbes disease

GSD 3 is an inherited disorder that causes a buildup of glycogen in specific organs and tissues – especially in the liver and muscles. The AGL gene is mutated which leads to a deficiency in the debrancher enzyme. The key to the breakdown of glycogen. It is inherited in an autosomal recessive manner and symptoms typically present in infancy, but may only occur in adulthood. Children are often diagnosed because they have a swollen abdomen due to a very large liver. Patients may also have low blood sugar, high ketones, a high level of fats in the blood, and delayed growth. Symptoms related to liver disease and progressive cardiac and skeletal muscle involvement vary in age of onset, rate of disease progression, and severity.

Type IV - Andersen's disease

Andersen disease (GSD 4) is a multisystem disorder that may affect the liver, voluntary (skeletal) muscles, the heart, the nervous system, and other bodily tissues. Disease nature and course may vary in several aspects, including age at onset, associated symptoms and signs, degree of abnormal glycogen accumulation in various tissues, and specific organs affected. Several neuromuscular variants have been described. These may be evident at birth, in late childhood, or adulthood. Deficient activity of the glycogen-branching enzyme is causing the disease. It results in accumulation of abnormal glycogen in the liver, muscle and other tissues.

Type VI - Her's Disease

GSD 6 is a disease due to a defective enzyme preventing glucose from being released from liver glycogen properly. As a result glycogen continues to build up in the liver. The liver becomes enlarged and swollen abdomen and produces symptoms of low blood sugar. Patients with GSD 6 have milder and shorter periods of low blood sugar, since they also can also make glucose from protein. In childhood the initial symptoms are a swollen abdomen due to an enlarged liver, a history of poor growth or short stature, frequent feeding, episodes of low blood sugar (hypoglycaemia) on fasting, and excessive tiredness following activity. However, with good dietary management, people with GSD 6 can lead a normal life, can have unaffected children and should live into old age. Potential complications in later life can include cirrhosis (scarring) and/or adenomas on the liver. Pregnancy should be closely monitored. Symptom may lessen as they become adults.

Type IX

GSD 9 is now recognized as one of the most prevalent forms of GSD, accounting for 25% of all persons affected by GSD. There are 4 variants, known as 9a, 9b, 9c and 9d. In GSD 9 the inheritance patterns are X-linked recessive which means that male children (sons) have a 50-50 percent risk of inheriting the mothers defect X-chromosome. Female children (daughters) can instead be unaffected carriers, or they inherit the functional X-chromosome and do not get the disease at all.

GSD type 9 is a disorder in which the body cannot break down (metabolize) glycogen (a complex form of sugar). In persons with GSD 9, glycogen is stored primarily in the body (liver and muscles, rarely in the heart) instead of being used.

Hypoglycemia is usually less severe than in the more severe forms of glycogen storage disease, GSD type 1, and therefor considered a mild disease. Yet there is a spectrum of severity in clinical manifestations and some patients can have life threatening hypoglycemia. Ketosis is usually a prominent metabolic feature in GSD 9, which is partially due to increased fatty acid oxidation as a compensation for low energy. Hepatomegaly (enlarged liver) is the most common feature in patients with GSD 9. Growth retardation is also common. Patients are often diagnosed with the liver enzyme transaminase elevation, hyperlipidemia, and/or ketotic hypoglycemia are found during laboratory evaluation for failure to thrive or during an acute illness. Sleep difficulties and overnight irritability are also common.

 

General symptoms of GSD may include

Not Growing fast enough

Not feeling comfortable in hot weather (heat intolerance)

Low blood sugar (hypoglycemia)        

Weak muscles (low muscle tone)              

Muscle pain and cramping during excersice

The symptoms of GSD may look like other health problems. Always see your child’s healthcare provider to be sure. Some types of GSD can appear in adults. See your healthcare provider if you think you may have GSD.

What causes Glycogen Storage Disease in a child?

Glycogenoses are caused by gene mutations in the body. Because of this the mutations lead to a lack of the enzymes needed to build up or break down glycogen.

Who is at risk for Glycogen Storage Disease?

GSD is normally passed down from parents to children (hereditary). For most types of GSD, both parents are unaffected carriers, meaning they carry one copy of a misspelled gene that can cause GSD paired with a normal copy of the gene. When both parents pass the misspelled gene to a child, the child has no normal copy of that gene and therefore develops GSD. In most cases GSD is diagnosed within the first year of life, but in some cases the diagnosis may not be made until later in childhood.

Someone who is a carrier of a GSD normally has no symptoms of the condition.

How is Glycogen Storage Disease diagnosed?

The diagnosis of GSD is made based on clinical manifestations and gene testing. Sometimes, a muscle or liver biopsy may be necessary in order to confirm the diagnosis.

How is Glycogen Storage Disease treated?

Currently, there is no cure for GSD. Types of GSD are grouped by the enzyme that is missing in each one. Treatment will vary depending on type of GSD. However, the overall goal is to maintain the proper level of glucose in the blood so that the cells have the fuel they need to prevent long-term complications. Until the early 1980s, children with GSDs had few treatment options and none were very helpful. Then it was discovered that ingesting uncooked cornstarch regularly throughout the day helped these children maintain a steady, safe glucose level. Cornstarch is a complex carbohydrate that is difficult for the body to digest; therefore it acts as a slow release carbohydrate and maintains normal blood glucose levels for a longer period of time than most carbohydrates in food.

Cornstarch therapy is combined with frequent meals (eating every two to four hours) of a diet that restricts sucrose (table sugar), fructose (sugar found in fruits) and lactose (milk sugar). Typically, this means no fruit, juice, milk or sweets (cookies, cakes, candy, ice cream, etc.) are allowed because these sugars end up as glycogen trapped in the liver. Infants need to be fed regularly both day and night (about every two hours). Those who are not breastfed must take lactose-free formula.

Some types of GSD require a high-protein diet. Calcium, vitamin D and iron supplements may be recommended to avoid deficits.

Children need their blood glucose tested (and ketones for ketotic types 0, 3, 6, 9) frequently throughout the day/night to make sure they are not hypoglycemic, which can be dangerous. 

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