Aldolase A Deficiency (in the form of glycogen storage disease)
What else is it called?
- Aldolase deficiency red cell
- Glycogen storage disease type 12
- Glycogen storage disease 12
- Glycogen storage disease type XII
- Glycogenosis due to aldolase A deficiency
- Glycogenosis type 12
- Glycogenosis type XII
- Glycogen storage disease due to Aldolase A deficiency
- Red cell Aldolase deficiency
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What causes it?
Aldolase A deficiency is an extremely rare glycogen storage disease. This disorder is caused by a problem in the ALD gene which is responsible for coding the ALD enzyme.
Glucose gets stored in the body as glycogen which is then used to provide energy for the body. When there is a lack or absence of the enzyme, aldolase A which is responsible for producing or breaking down glycogen, the glycogen storage disease occurs. The Aldolase A enzyme is found mainly in muscles and red blood cells. When there is a lack of this enzyme, haemolytic anaemia will occur. This is when not enough red blood cells are being made by the bone marrow to replace those that are being destroyed.
How common is it?
This disorder is extremely rare and only 6 cases have been reported.
What are the signs and symptoms?
Most common symptoms:
- Myopathy (disease of the muscles, resulting in muscular weakness)
- Rhabdomyolysis (the breakdown of damaged skeletal muscle tissue)
- Haemolytic anaemia (abnormal breakdown of red blood cells)
- Convulsions (sudden irregular movement of the body)
- Excessive sleepiness
- Poor feeding as a baby
- Problems after eating fruits and fructose/sucrose-containing foods
- Exercise intolerance
- Premature muscle fatigue
- Muscle weakness
- Jaundice (yellowish tinge to the skin and the whites of the eyes)
- Reduced muscle mass
- Reduced muscle tone
- Enlarged liver
- Liver disease (in severe cases)
- Enlarged spleen
- Mental retardation
The age of onset of this disorder is usual neonatal (newborn).
The disorder causes myopathy which will result in rhabdomyolysis (breakdown of damaged muscle fibres) and then results to releasing the contents of the muscle breakdown into the bloodstream. Myopathy is usually first recognized through muscle weakness and exercise intolerance.
A case of Aldolase A Deficiency has been reported where haemolytic anaemia was not present.
How is it diagnosed?
The disorder is diagnosed through specialised urine and blood tests. Elevated galactose levels will be detected in the urine and is confirmed by enzyme analysis of red blood cells, hepatic tissue or both.
Aldolase A deficiency is currently not included in newborn screening in the UK or USA.
Can it be treated?
Treatment includes removal of all sources of galactose in the diet, mainly lactose. Lactose is present in all dairy products (including milk-based baby formulas). Please be noted that any dietary changes require specialist dietitian’s advice and monitoring. A lactose-free diet can prevent toxicity; however, it may not prevent neurocognitive problems.
Red blood cell transfusion can also be used as a supportive measure when patients have severe anaemia. Spleen removal can sometimes also improve anaemia.
The prognosis of Aldolase A deficiency can vary from relatively mild to very severe. In most cases, children following a diet avoiding fructose and sucrose will produce positive results. However, a few children will develop severe liver disease. In severe case, even following a fructose and sucrose free diet may not prevent severe liver disease.
Do my family need to be tested?
Aldolase A deficiency 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 Aldolase A deficiency 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 Aldolase A deficiency 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.