Glycogen storage disease (type 1a) is a condition characterized by abnormally low blood sugar levels, enlarged liver and kidneys, and impaired growth – that results from the build-up of stored glycogen in the body. The main symptoms can be treated with strict dietary management.
If you have just received a diagnosis there is help and support available – please see ‘Further information and support’ below for links to valuable resources. It is also important to note that not every person with this condition experiences all the symptoms described and it is worth talking to your doctor or other relevant healthcare specialists to discuss you or your family member’s specific case.
Glycogen storage disease (type 1a) is an autosomal recessiveRecessive disorders require both parents to carry a specific disorder-related mutation and pass it on to their child for the disorder to be inherited condition.
The carrier frequency of GSD1a among Ashkenazi Jews is approximately 1 in 70. The disease frequency is around 1 in 20,000 Ashkenazi Jews as compared to 1 in 500,000 in the general population.
Symptoms of GSD1a are typically seen in the first few months of a child’s life. Common signs and symptoms of the disease include:
- Abdominal swelling – due to enlarged liver
- Very low blood sugar levels (severe hypoglycaemia) – that can lead to irritability, lethargy or shakiness
- Prolonged hypoglycaemia can lead to seizures
- Poor growth leading to short stature.
- Abnormally high levels of fats and of lactic acid in the blood
- Muscle weakness with delay in walking
If the condition is untreated, long-term complications can include:
- Fragile bones
- Delayed puberty
- Bleeding problems
- Renal disease
- Benign liver tumours
- Polycystic ovaries
- Disease of the pancreas
- Development delay can occur as a secondary effect of chronic hypoglycaemia.
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The disease is caused by changes in a gene that lead to a severe deficiency in the production of the enzyme D-glucose-6-phosphatase (G6Pase) which is essential in the breakdown of glycogen.
Glycogen is a carbohydrate which acts as a primary energy reserve for the body. When exercising or fasting, glycogen is broken down into glucose, which can then be metabolized to release energy. As a result of this enzyme deficiency, harmful amounts of glycogen build up in the liver and kidneys. The body suffers from low blood sugar as it is unable to release energy from its glycogen energy stores.
Research has shown that in the Ashkenazi Jewish community one specific mutation is responsible for almost all cases of GSD1a.
Symptoms can be effectively treated with a strictly managed diet. Low blood sugar levels are controlled by frequent day time meals of measured amounts of carbohydrate. In most cases, a glucose supply is given throughout the night via a gastric tube. As affected children get older, taking regular doses of corn-starch which breaks down slowly in the body releasing a constant supply of glucose can be a very effective treatment. With intensive treatment most complications of this disorder can be prevented.
Other drugs and treatments are available to alleviate other symptoms associated with the condition such as gout, kidney disease and increased levels of lipid in the blood. Benign liver tumours occur extremely rarely now with modern dietary treatment. Patients are monitored regularly with ultrasound scans to check for their occurance.
Gene therapy trials which aim to replace the faulty gene in the liver are just starting in sdult patients but are experimental at present.
With effective treatment from an early age, those affected by GSD1a can have a normal life expectancy and can also experience normal growth and puberty.
GSD1a is usually diagnosed clinically by a doctor familiar with the symptoms, and with a blood test to measure the levels of glucose, lactic acid and lipids. Rarely a liver biopsy will be taken to measure the G6Pase enzyme activity. Genetic testing, using a simple blood test, can be carried out to confirm the diagnosis.
Carrier testing and prenatal diagnosis for GSD1a are also now possible, though since the disorder can be treated, appropriate counselling is vital. Overall the detection rate for carriers of Ashkenazi Jewish ancestry is approximately 99%.
For more details about testing, please refer to the testing section.
The AGSD is a parent and patient oriented support group that covers all different types of GSD. Advised by a group of experienced medical professionals, the organisation raises awareness and educates others, as well as publishing a quarterly newsletter – The Ray.
To find out more about general resources relevant to Jewish genetic disorders, please visit our resources and support section.
Written by Jnetics.
Approved by Dr Helen Mundy, Consultant Metabolic Paediatrician, Evelina Children’s Hospital, Guys and St Thomas NHS Foundation Trust.
Last review date: 27.06.2018