Glycogen Storage Disease

Glycogen storage disease is a rare genetic disorder affecting 1 in 100,000 newborns. Glycogen storage diseases (GSDs) are a group of disorders where abnormal storage or release of glycogen leads to potentially life-threatening hypoglycemia and metabolic disturbances. Dietary interventions have markedly improved the outcome for these disorders, from a previously fatal condition to one where people can do well with proper care. 

Source: Dr. David Weinstein, Director, Glycogen Storage Disease Program, Connecticut Children’s. The world leading GSD expert Dr. David Weinstein it sitting in the Ketotic Hypoglycemia International Scientific Advisory Board. 

Type 0

Glycogen storage disease type 0 (also known as GSD 0) is a condition caused by the body’s inability to form a complex sugar called glycogen , which is a major source of stored energy in the body. 

Symptoms

  • Muscle pain0
  • Arrhytmia
  • Weaknes/fainting
  • Ketotic hypoglycemia

GSD 0 has two types: in muscle GSD 0, glycogen formation in the muscles is impaired, and in liver GSD 0, glycogen formation in 

The liver is in the upper abdomen near the stomach, intestines, gallbladder, and pancreas. The liver has four lobes. Two lobes are on the front and two small lobes (not shown) are on the back of the liver.

The signs and symptoms of muscle GSD 0 typically begin in early childhood. Affected individuals often experience muscle pain and weakness or episodes of fainting (syncope) following moderate physical activity, such as walking up stairs. The loss of consciousness that occurs with fainting typically lasts up to several hours. Some individuals with muscle GSD 0 have a disruption of the heart’s normal rhythm (arrhythmia) known as long QT syndrome. In all affected individuals, muscle GSD 0 impairs the heart’s ability to effectively pump blood and increases the risk of cardiac arrest and sudden death, particularly after physical activity. Sudden death from cardiac arrest can occur in childhood or adolescence in people with muscle GSD 0.

Individuals with liver GSD 0 usually show signs and symptoms of the disorder in infancy. People with this disorder develop low blood sugar (hypoglycemia) after going long periods of time without food (fasting). Signs of hypoglycemia become apparent when affected infants begin sleeping through the night and stop late-night feedings; these infants exhibit extreme tiredness (lethargy), pale skin (pallor), and nausea. During episodes of fasting, ketone levels in the blood may increase (ketosis). Ketones are molecules produced during the breakdown of fats, which occurs when stored sugars (such as glycogen) are unavailable. These short-term signs and symptoms of liver GSD 0 often improve when food is eaten and sugar levels in the body return to normal. The features of liver GSD 0 vary; they can be mild and go unnoticed for years, or they can include developmental delay and growth failure.

(https://ghr.nlm.nih.gov/condition/glycogen-storage-disease-type-0

 

Type III

Glycogen storage disease type III (also known as GSDIII or Cori disease) is an inherited disorder caused by the buildup of a complex sugar called glycogen in the body’s cells.

Symptoms:

  • Hyperlipidemia (fat in the blood)
  • Hepatomegaly (enlarged lever)
  • Ketotic hypoglycemia
  • Elevated lever enzymes
  • Slow growth

The accumulated glycogen is structurally abnormal and impairs the function of certain organs and tissues, especially the liver and muscles.

GSDIII is divided into types IIIa, IIIb, IIIc, and IIId, which are distinguished by their pattern of signs and symptoms. GSD types IIIa and IIIc mainly affect the liver and muscles, and GSD types IIIb and IIId typically affect only 

The liver is in the upper abdomen near the stomach, intestines, gallbladder, and pancreas. The liver has four lobes. Two lobes are on the front and two small lobes (not shown) are on the back of the liver.

It is very difficult to distinguish between the types of GSDIII that affect the same tissues. GSD types IIIa and IIIb are the most common forms of this condition.

Beginning in infancy, individuals with any type of GSDIII may have low blood sugar (hypoglycemia), excess amounts of fats in the blood (hyperlipidemia), and elevated blood levels of liver enzymes. As they get older, children with this condition typically develop an enlarged liver (hepatomegaly). Liver size usually returns to normal during adolescence, but some affected individuals develop chronic liver disease (cirrhosis) and liver failure later in life. People with GSDIII often have slow growth because of their liver problems, which can lead to short stature. In a small percentage of people with GSDIII, noncancerous (benign) tumors called adenomas may form in the liver.

Individuals with GSDIIIa may develop muscle weakness (myopathy) later in life. These muscle problems can affect both  and the muscles that are used for movement. Muscle involvement varies greatly among affected individuals. The first signs and symptoms are typically poor muscle tone (hypotonia) and mild myopathy in early childhood. The myopathy may become severe by early to mid-adulthood. Some people with GSDIIIa have a weakened heart muscle (cardiomyopathy), but affected individuals usually do not experience heart failure. Other people affected with GSDIIIa have no cardiac muscle problems.

(https://ghr.nlm.nih.gov/condition/glycogen-storage-disease-type-iii)

Type VI

Glycogen storage disease type VI (also known as GSDVI or Hers disease) is an inherited disorder caused by an inability to break down a complex sugar called glycogen in liver cells.

Symptoms: 

  • Hepatomegaly (enlarged lever)
  • Ketotic hypoglycemia
  • Slow growth
  • Mild delays in development of motor skills

The accumulated glycogen is structurally abnormal and impairs the function of certain organs and tissues, especially the liver and muscles.

GSDIII is divided into types IIIa, IIIb, IIIc, and IIId, which are distinguished by their pattern of signs and symptoms. GSD types IIIa and IIIc mainly affect the liver and muscles, and GSD types IIIb and IIId typically affect only 

The liver is in the upper abdomen near the stomach, intestines, gallbladder, and pancreas. The liver has four lobes. Two lobes are on the front and two small lobes (not shown) are on the back of the liver.

It is very difficult to distinguish between the types of GSDIII that affect the same tissues. GSD types IIIa and IIIb are the most common forms of this condition.

Beginning in infancy, individuals with any type of GSDIII may have low blood sugar (hypoglycemia), excess amounts of fats in the blood (hyperlipidemia), and elevated blood levels of liver enzymes. As they get older, children with this condition typically develop an enlarged liver (hepatomegaly). Liver size usually returns to normal during adolescence, but some affected individuals develop chronic liver disease (cirrhosis) and liver failure later in life. People with GSDIII often have slow growth because of their liver problems, which can lead to short stature. In a small percentage of people with GSDIII, noncancerous (benign) tumors called adenomas may form in the liver.

Individuals with GSDIIIa may develop muscle weakness (myopathy) later in life. These muscle problems can affect both  and the muscles that are used for movement. Muscle involvement varies greatly among affected individuals. The first signs and symptoms are typically poor muscle tone (hypotonia) and mild myopathy in early childhood. The myopathy may become severe by early to mid-adulthood. Some people with GSDIIIa have a weakened heart muscle (cardiomyopathy), but affected individuals usually do not experience heart failure. Other people affected with GSDIIIa have no cardiac muscle problems.

(https://ghr.nlm.nih.gov/condition/glycogen-storage-disease-type-iii)

Type IX

Glycogen storage disease type IX (also known as GSD IX) is a condition caused by the inability to break down a complex sugar called glycogen. 

Symptoms: 

  • Hepatomegaly (enlarged lever)
  • Ketotic hypoglycemia
  • Slow growth
  • Mild delays in development of motor skills
  • Delayed puberty
  • Muscle pai

The different forms of the condition can affect glycogen breakdown in liver cells or muscle cells or sometimes both. A lack of glycogen breakdown interferes with the normal function of the affected tissue.

When GSD IX affects the liver, the signs and symptoms typically begin in early childhood. The initial features are usually an enlarged liver (hepatomegaly) and slow growth. Affected children are often shorter than normal. During prolonged periods without food (fasting), affected individuals may have low blood sugar (hypoglycemia) or elevated levels of ketones in the blood (ketosis). Ketones are molecules produced during the breakdown of fats, which occurs when stored sugars are unavailable. Affected children may have delayed development of motor skills, such as sitting, standing, or walking, and some have mild muscle weakness. Puberty is delayed in some adolescents with GSD IX. In the form of the condition that affects the liver, the signs and symptoms usually improve with age. Typically, individuals catch up developmentally, and adults reach normal height. However, some affected individuals have a buildup of scar tissue (fibrosis) in the liver, which can rarely progress to irreversible liver disease (cirrhosis).

GSD IX can affect muscle tissue, although this form of the condition is very rare and not well understood. The features of this form of the condition can appear anytime from childhood to adulthood. Affected individuals may experience fatigue, muscle pain, and cramps, especially during exercise (exercise intolerance). Most affected individuals have muscle weakness that worsens over time. GSD IX can cause myoglobinuria, which occurs when muscle tissue breaks down abnormally and releases a protein called myoglobin that is excreted in the urine. Myoglobinuria can cause the urine to be red or brown.

In a small number of people with GSD IX, the liver and muscles are both affected. These individuals develop a combination of the features described above, although the muscle problems are usually mild.

(https://ghr.nlm.nih.gov/condition/glycogen-storage-disease-type-ix)