Primary Carnitine Deficiency

What else is it called?

  • Carnitine Transporter Deficiency 
  • Carnitine Uptake Defect 
  • Carnitine Uptake Deficiency 
  • CUD 
  • Renal Carnitine Transport Defect 
  • Systemic Carnitine Deficiency 

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What causes it?

Primary Carnitine deficiency is caused by a fault in the gene (SLC22A5) which is inherited from your parents. This gene is involved in the production of a protein called OCTN2 which transports carnitine into the body’s cells. Carnitines role is to bind and transfer fatty acids into your cells, fatty acids are a major energy source for the body. Primary Carnitine deficiency means that you are unable to transfer fatty acids into your body’s cells to be broken down and used for energy. 

During periods of fasting or during bouts of illness such as infection, your blood sugars may become depleted. In this instance, your body will attempt to break down fatty acids for it to be used as an energy source. However, with Primary Carnitine deficiency you cannot transfer the fatty acids into the cells to be broken down due to the reduced or absent levels of carnitine. This metabolic disorder may lead to low levels of blood sugars and possible acute episodes of hypoglycaemia. 

If diagnosed, medication will be prescribed to increase the level of carnitine within your body. The avoidance of prolonged periods of fasting is recommended as this can have serious health implications on your body. 

How common is it?

Primary Carnitine deficiency currently affects 1 in every 100,000 new-borns. This metabolic disorder yields a higher prevalence within areas of Japan. It has been estimated to affect 1 in every 40,000 new-borns within this geographical area. 


What are the signs and symptoms?

Signs and symptoms can be varied and can be specific to the diagnosed individual. Symptoms can present in a mild or in a severe form. 

Signs and symptoms for the metabolic condition, Primary Carnitine deficiency include: 

  • Lethargy/tiredness/fatigue 
  • Poor food intake/ feeding 
  • Brain damage 
  • Confusion 
  • Acute and chronic seizures 
  • Vomiting 
  • Levels of carnitine within blood sample below normal threshold values 
  • Insufficient weight gain or weight loss 
  • Heart complications/ weakened heart muscle 
  • Low blood sugars/ hypoglycaemia due to prolonged low blood sugar levels 


How is it diagnosed?

In some countries this condition is screened for as part of a newborn screening test which allows for early intervention by course of dietary changes and management. This method of testing has proven beneficial in the avoidance of heart complications.  

Diagnosis for this condition is usually confirmed when symptoms first present, usually between the ages of 2 months to 2 years old and involves a range of specialised blood and urine tests, a clinical examination and a detailed patient and family history.  

Can it be treated?

Primary Carnitine deficiency is primarily treated with Levocarnitine. Levocarnitine is a form of the natural occurring substance L-carnitine, a transporter protein which enables the cells within your body to fulfil energy requirements. Medication containing the L-carnitine form of carnitine is preferred by specialists, as it has a higher absorption rate across the small intestine and blood brain barrier compared to other forms of carnitine. Levocarnitine works by flooding the body with carnitine, which in turn means your body can transport fatty acids into the cells of your body for them to be metabolised for energy. Following on from prescription, a post routine blood test will follow every 4-6 months, this is to ensure that the dosage of Levocarnitine prescribed is the right amount for you. Dosage will be adjusted accordingly by your health care professional if carnitine count is found to be above or below the required threshold values. L-carnitine has proven to assert many other health beneficial qualities such as, reversing underlying heart problems, aid the removal of toxic substances from the body and actively reduce muscle weaknesses.  

Although Levocarnitine is deemed the primary treatment for this condition, diet is an important contributing aspect to consider regarding the management of Primary Carnitine deficiency. Your assigned dietitian will be involved throughout the management of your condition and may incorporate a high carbohydrate, low fat diet. Vegan and vegetarian diets are not permitted for this condition, as foods such as red meat, dairy products and poultry yield dietary sources of carnitine within them. Dietary carnitine can be ingested and absorbed by the body for effective fatty acid metabolism.  

An array of symptoms can present due to this condition two of which are, bouts of vomiting and sickness which subsequently, cause energy levels to rapidly deplete. Drinking a high sugar drink such as Lucozade is advised if the above examples occur to avoid low blood sugars caused by energy depletion and in instances of fasting. An IV glucose drip can sometimes be a prescribed measure to avoid low blood sugars possibly during bouts of vomiting, sickness or during episodes of fasting. Your dietitian will be able to help you with the management of your condition, they will be on hand to assist with anything you may require and answer any question you may have about your diagnosis. By prescribing Levocarnitine and applying dietary changes, a person diagnosed with Primary Carnitine Deficiency can go on to live a very normal life. 

Do my family need to be tested?

Primary carnitine 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 Primary carnitine 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. 


Relevant Organisations


References are available on request. Please contact Helen Morris by phoning 0845 241 2173 or emailing [Resource Library No: PFKB11]. 

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