Glycogen storage disease type III
What are the main signs and symptoms of glycogen storage disease type 3?
Glycogen storage disease type III (GSD III) typically presents with liver problems first. In babies, the liver may be enlarged and lab studies to look at liver function may be abnormal. If GSD III is not treated, babies can have low blood sugar, enlarged liver, muscle weakness, delayed growth and development, sleepiness and irritability. If a baby is not treated properly when symptoms develop, these symptoms can progress to seizures, coma or even death. Symptoms usually improve with frequent feeding (every 3-4 hours) and avoidance of becoming ill. When a person with GSD III becomes ill, close medical monitoring is needed to ensure that symptoms do not get worse and that the person is safe.
During adolescence, the liver tends to shrink and liver problems may become milder. Many people with GSD IIIa subtype, may also experience muscle weakness in adolescence and adulthood. Because the heart is a muscle, GSD III can also result in weakness of the heart muscle (hypertrophic cardiomyopathy) that may need to be followed closely by a specialist.
If your child with GSD III is experiencing any symptoms of low blood sugar or is sick with a fever, vomiting or diarrhea, consult with your main doctor or genetic/metabolic doctor. It may be important for your child to get emergency treatment.
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When do the symptoms of glycogen storage disease type 3 start?
Babies with glycogens storage disease type III are often born healthy at birth and may not have any signs or symptoms of the condition. In some people symptoms may not start until early childhood; however, other people can have symptoms as early as 3 or 4 months old, as babies begin to get less frequent feedings. The first signs are often an enlarged liver and low blood sugar. Lab studies may also show abnormally high levels of liver enzymes.
By puberty the liver tends to shrink in size and become less of a concern. In adolescence and young adulthood, many people experience muscle weakness and a type of heart condition known as hypertrophic cardiomyopathy, when the heart muscle becomes unusually thick. Many people with thick heart muscles have no symptoms and no medical issues but should be followed closely by a heart doctor. In some people, dietary changes can improve the heart thickness.
What health problems should I look for if my child has glycogen storage disease type 3?
People with glycogen storage disease type III (GSD III) cannot break down glycogen stored in the liver and muscles. In babies healthy at birth and may not have any signs or symptoms of the condition. The first signs are often an enlarged liver and low blood sugar. Lab studies may also show abnormally high levels of liver enzymes.
While the liver size typically shrinks over time, some people with GSD III get non-cancerous (benign) tumors on their liver. In some people, the liver problems can progress throughout life and may require a liver transplant.
As people with GSD III get older many of them experience muscle weakness. In childhood, many people with GSD III can develop a condition called hypertrophic cardiomyopathy. This is a condition where the heart muscles become unusually thick. Usually, the cardiomyopathy does not cause any symptoms or lasting health problems for people with GSD III. Occasionally, this finding can result in the heart not functioning as well as it does normally.
All people with GSD III regardless of symptoms should get regular examinations of their liver, heart and blood to monitor for any problems. In order to learn whether a health problem is related to GSD III or not, people can ask the main doctor or genetic doctor who best understands their health issues.
Are there other disease that look like glycogen storage disease type 3?
Glycogen storage disease type III (GSD III) is a type of glycogen storage disease. People with glycogen storage diseases are unable to use or store glycogen. Instead of providing energy between meals, the glycogen builds up and causes problems throughout the body. The health problems seen in GSD III can look like those seen in some other glycogen storage diseases. Each type of GSD is caused by changes in different genes. Only changes in the AGL gene cause GSD III.
Also, there are three main findings (enlarged liver, low blood sugar and high liver enzymes) that are seen in GSD III, that can make it look different from other types of GSDs. Certain blood tests, such as a genetic test, may help determine if a person has GSD III. The best person to help figure out if someone is having symptoms of GSD III or another type of glycogen storage disease is a genetic or metabolic doctor, a doctor specially trained to diagnose and treat genetic conditions and related conditions of the metabolic (energy-making) system. Genetic doctors in an area can be found by talking to another doctor about who they would recommend or by using the "Find A Genetic Service" tool at the American College of Medical Genetics.
- Dagli A, Sentner CP, Weinstein DA. Glycogen Storage Disease Type III. 2010 Mar 9 [Updated 2012 Sep 6]. In: Pagon RA, Adam MP, Ardinger HH, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2016. Available from: http://www.ncbi.nlm.nih.gov/books/NBK26372/