Glycogen Storage Disease Type XI (Fanconi Bickel Syndrome)
What else is it called?
- Fanconi Bickel
- Fanconi Bickel Syndrome
- Lactate Dehydrogenase
- Hepatorenal glycogenosis with renal Fanconi syndrome
- Hepatic glycogenosis with amino aciduria and glucosuria
- Fanconi syndrome with intestinal malabsorption and galactose intolerance
- Pseudo-Phlorizin diabetes
- Glycogenosis Fanconi type
- Glycogen storage disease XI
- GLUT2 deficiency
- Glycogen storage disease due to GLUT2 deficiency
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What causes it?
Glycogen Storage Disease Type XI is caused by mutations (changes) in the SLC2A2 gene. This gene is responsible for telling the body how to make a protein called glucose-transporter protein 2 (GLUT2). This protein transports glucose through different cells in the body.
When mutations (changes) happen in the SLC2A2 gene, GLUT2 does not work properly so the body cannot transport glucose. This causes glucose to build-up in the liver and kidneys. This glucose is then stored as glycogen which will build up and cause the symptoms associated with the condition.
How common is it?
The exact prevalence of this condition is unknown, but less than 200 cases have been reported to date worldwide.
What are the signs and symptoms?
This disorder is characterized by the build-up of glycogen in the liver and kidneys which causes symptoms such as:
- Rickets (weakened bones)
- Being very small for one’s age (failure to thrive)
- renal tubular dysfunction (specific type of kidney malfunction)
- hepatosplenomegaly (swelling of the liver and spleen)
- Hypoglycaemia (low blood sugar between meals)
- Entering puberty later than expected
The following symptoms may occur in adulthood:
- Osteopenia (a condition that begins as you lose bone mass and can lead to osteoporosis)
- Osteoporosis (a disease which reduced bone density and quality)
- Bowed legs
- Short stature (below average height)
How is it diagnosed?
Glycogen storage disease is diagnosed through a clinical examination based on the symptoms of the condition. Symptoms that may be identified in the clinical evaluation include rickets (weakened bones) and high levels of glucose, protein and phosphate in the urine (through specialised urine tests).
Specialised blood tests can also be done to show low levels of phosphate and high levels of cholesterol in the blood. People with this condition also tend to have low blood sugar between meals.
The diagnosis can be confirmed through molecular genetic testing which will show mutations (changes) in the SLC2A2 gene.
Can it be treated?
Treatment of this condition aims at treating the signs and symptoms of the condition. For example, for treatment of kidney disease, a doctor may replace water and electrolytes that are lost from the kidneys. Vitamin D and phosphate supplements can also be used to help prevent rickets (bone weakening).
Treatment also includes following a galactose-restricted diet. Galactose is broken down into glucose. Because people with glycogen storage disease type XI have difficulties moving glucose throughout the body, decreasing the amount of galactose stops the build-up of glucose and glycogen in the liver and kidneys. Galactose is found in foods including milk, cheese, yoghurt and legumes (beans, peas, lentils etc). People with this condition should eat fructose as their main carbohydrate. They should also eat small and frequent meals to prevent low blood sugars between meals. Corn starch may be used as a replacement to provide the body with the necessary sugars. Please be noted that any dietary changes require specialist dietitian’s advice and monitoring.
These treatments may improve some of the signs and symptoms associated with the condition. Kidney disease and the swelling of the liver and spleen usually resolve before adulthood. Dietary treatments usually do not improve growth with can lead to short stature in adulthood.
With proper treatment, some of the symptoms can resolve with age and individuals with this condition have been reported to reach adulthood and have children of their own.
Do my family need to be tested?
Glycogen storage disease type XI is an inherited condition. Humans have chromosomes made up of DNA. Genes are pieces of DNA that carry the genetic information. Each chromosome may have several thousand genes. We inherit chromosomes from the egg of the mother and sperm of the father. The genes on those chromosomes carry the instructions that determine a person’s characteristics, which are a combination of the parents.
The pattern of inheritance of glycogen storage disease type XI is autosomal recessive. This means that carriers of the condition do not have the disorder because the other gene of this pair is working normally. Parents of children with glycogen storage disease type XI are carriers.
When both parents are carriers, the risk to the baby in each pregnancy is
- 25% chance (1 in 4) of developing the condition
- 50% chance (1 in 2) for the baby to be a carrier of the condition
- 25% chance (1 in 4) for the baby to have two working genes and neither have the condition nor be a carrier
Genetic counselling can be requested to get a full explanation.
For more information, please visit Association for Glycogen Storage Disease UK.