Hereditary Folate Malabsorption
What else is it called?
- Congenital folate malabsorption
- Congenital defect of folate absorption
- Folic acid transport defect
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What causes it?
Folate plays a crucial role in the production of your DNA and RNA which are involved in the production of protein. Protein is used by your body to build and repair muscle.
Hereditary folate malabsorption is caused by a defect in a gene (SLC46A1) which you inherit from your parents. This gene usually codes for a protein (PCFT) that is located within your small intestine. The PCFT protein allows your body to transport folate you obtain from diet and absorb it through your small intestine, into your blood stream and into your brain via your Cerebrospinal Fluid (CSF) to be used for cognitive development.
However, due to this gene defect your body is unable to transport and absorb folate or may only be able to in small amounts.
How common is it?
Prevalence of Hereditary Folate Malabsorption is currently unknown. Approximately 15 families have been reported worldwide as having Congenital folate malabsorption. There is no evidence to suggest there is a greater prevalence in any country or between males and females.
What are the signs and symptoms?
One of the main symptoms of Hereditary folate malabsorption is a condition called megaloblastic anaemia. Megaloblastic anaemia is characterised as having low levels of red blood cells in your blood stream. The blood cells are referred to as megaloblastic due to their large appearance. Their appearance is due to the red blood cells not fully maturing for function in bone marrow and because of their size, many of them are too large to leave and enter your blood stream. This leads to a low level of red blood cells and oxygen circulating in the blood stream.
Other signs and symptoms to look out for with Hereditary folate malabsorption are:
- Episodes of diarrhoea
- Lack of weight gain
- Cognitive and physiological development delays
- Pale skin
If diagnosed with Hereditary folate malabsorption, a lack of white blood cells may be circulating in the body. White blood cells are important for fighting off bugs and infection. A white blood cell deficiency creates a higher risk of getting an infection. There is also the possibility of platelet deficiency. Platelets are what cause blood to stop bleeding via clotting. Alow platelet count means that bleeding and bruising may occur more easily than usual.
Symptoms of Hereditary folate malabsorption tend to present in very early infancy. This is due to folate being obtained from the mother whilst she is pregnant. Therefore, levels of folate can remain adequate in the body until birth when the supply of folate is stopped once the umbilical cord is cut.
How is it diagnosed?
If a doctor sees signs of Hereditary folate malabsorption they may perform a full blood count test to check levels within the blood stream. This will be checked against baseline values to see if a deficiency such as anaemia is present.
A doctor may also perform a blood test to check for any abnormalities. with your red blood cells, platelets and white blood cells.
Another test the doctor may perform is a reticulocyte count to test whether bone marrow is producing enough red blood cells for the body to use to carry oxygen.
This condition can also be confirmed by genetic testing prior to birth. This test would check if there is a defect with the gene inherited that makes the PCFT protein. Early diagnosis of this condition is beneficial in avoidance of the risks this metabolic condition poses.
Can it be treated?
Due to the rare nature of this metabolic condition there is no current treatment available for the gene defect. Levels of folate can be raised in the blood by administering doses of folate parenterally.e.g. through intramuscular injections. This can improve levels of folate within the blood and CSF and decrease the level of anaemia and other symptoms.
Levofolinate is a drug that can be used to treat this condition by raising levels of folate within the body. A doctor will need to refer to a metabolic specialist for treatment options to be explored. To check that this treatment is working correctly, full blood counts can be undertaken, together with CSF samples obtained via a procedure called a Lumbar Puncture. Magnetic Resonance Imaging (MRI) scans can also be carried out to check the development of the brain.
Do my family need to be tested?
Hereditary folate malabsorption can only be passed on to a child if both parents have a copy of the faulty gene. This is called autosomal recessive inheritance. A person who has a copy of the faulty gene is known as a carrier.
If both parents are carriers, their child has a one in four (25%) chance of inheriting the disorder, and a one in two chance (50%) of being a carrier. This is the same for each child the parents have.
If the child only inherits one copy of the faulty gene, they will be a carrier but will not have the disorder. In some rare cases, carriers have had mild symptoms of the disorder for which they carry the faulty gene.
Following diagnosis, a referral can be made to a Genetic Counsellor who can explain more about how the condition manifested. They can also explain about genetic testing for family members. They can provide advice and support for family planning. Parents who have had a child diagnosed with Hereditary folate malabsorption and go on to have further children should ensure that a Newborn Screening test is carried out within 24-48 hours of birth.