Methylenetetrahydrofolate Reductase Deficiency

What else is it called?

  • MTHFR Deficiency 
  • 5,10-methylenetetrahydrofolate reductase deficiency 

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What causes it?

MTHFR deficiency is metabolic disorder that reduces or inhibits folate (folate may be referred to as Vitamin B9) metabolism. This condition is caused by a defect in the gene you inherit from your parents. This gene usually produces a substance called the MTHFR enzyme. This enzyme converts the inactive form of folate into the active form for the body to use. However, due to this gene deficiency the body cannot produce this enzyme to metabolise folate. 

This condition can lead to the accumulation of a harmful substance in your body called homocysteine. The MTHFR enzyme usually converts homocysteine into the amino acid methionine, an important building block for many proteins in your body. High levels of homocysteine in the blood can increase the chances of certain health risks. 

How common is it?

MTHFR deficiency is the most common metabolic disorder of folate metabolism. Currently there has been reports of 40 individuals with this disorder with no increased risk between males and females. 

What are the signs and symptoms?

Some of the signs and symptoms to look out for with this condition are:  

  • Developmental delays  
  • Low muscle tone   
  • Seizures  
  • Failure to thrive  
  • Blood clots  
  • Small head size  
  • Ataxia  
  • Peripheral neuropathy  
  • Scoliosis 
  • High urine homocysteine levels 

Other symptoms associated with this metabolic disorder are mental health and behavioural issues. 

If you have MTHFR then this may lead to an increase risk of cardiovascular disease or and thrombosis. This is due to the high levels of homocysteine that can occur with this condition, although these diseases are found to be very rare for people with MTHFR deficiency. 

If you have high levels of homocysteine within your body other factors should be considered which have shown to increase the levels of homocysteine, these are: 

  • Smoking
  • Hypothyroidism
  • Chronic conditions such as diabetes, obesity and high blood pressure
  • Certain type of medication

Medication such as atorvastatin, fenofibrate, methotrexate, and nicotinic acid have been shown to be harmful to the body if you have high levels of homocysteine. 


How is it diagnosed?

MTHFR deficiency can be diagnosed by obtaining a full blood sample from you. Your GP would take the full blood sample to measure the levels of homocysteine in your blood and the extent to which MTHFR is working. MTHFR would be diagnosed if levels of homocysteine are high and levels of the amino acid methionine were low. 

MTHFR can also be diagnosed by genetic testing. This would involve taking a blood sample from yourself to determine levels of the genes needed for MTHFR to work correctly. If these levels are low or absent, then this can mean you have MTHFR deficiency. This test may be requested when your family history includes cardiovascular disease, thrombosis or MTHFR deficiency. Currently, there is no allocation for genetic testing within the United Kingdom. 

Can it be treated?

Doses of betaine (Cystadane) have been shown to be effective with managing this condition. Betaine is an amino acid which is involved converting homocysteine in the blood into a less harmful form called methionine. The earlier treatment is started for this metabolic condition the more likely you are not to experience the symptoms. Later treatment does not reverse the symptoms associated with this condition, but they can improve the severity of them. 

It has also been suggested that doses of folate and vitamin B12 along with betanine can prevent the symptoms associated with methylenetetrahydrofolate reductase deficiency. For any more information regarding the management of this condition please contact your local GP. 

Do my family need to be tested?

MTHFR deficiency 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.  

Once you are diagnosed, you can speak to a genetic counsellor. They can explain how you may have inherited MTHFR deficiency. They can also tell you about genetic testing for the rest of your family. They can provide advice and support if you go on to have children of your own. If you have previously had a child with MTHFR deficiency and go on to have further children, their New-born Screening test should be carried out within 24-48 hours of birth. 

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