Lethal Infantile Mitochondrial Myopathy

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Lethal Infantile Mitochondrial Myopathy is caused by a problem in the MT-TT gene. This gene produces a molecule which helps to make protein in your cells. This process is needed because your cells need protein to continue to work and carry out their functions. 

If you have a problem in the MT-TT gene, you will not produce enough of the molecule used to make this protein. Therefore, your cells will not have the energy to function properly and this can cause a wide range of issues throughout your body. 

Lethal Infantile Mitochondrial Myopathy is an extremely rare disorder. There have only been three cases reported worldwide. 

Symptoms of the disorder typically begin within the first few days of life. They include: 

• Unusually low muscle tone (hypotonia) 
• Paralysis of muscles around the eye (progressive external ophthalmoplegia) 
• Below normal or absent reflexes (areflexia) 
• Severe build-up of lactate in the body (lactic acidosis) which causes fatigue and weakness 
• Lack of energy (lethargy) 
• Heart disease (cardiomyopathy) 
• Kidney and/or liver problems 
• Seizures

Life expectancy is short, and children with the disorder do not live beyond the first few months of life.

Diagnosis for Lethal Infantile Mitochondrial Myopathy is carried out using a specialised blood test. Genetic testing is required to confirm the disorder.  

Due to the speed at which this disorder causes deterioration, it is possible that Lethal Infantile Mitochondrial Myopathy is under-diagnosed and so there may be more cases than we currently know. It has also been suggested that this disorder may be responsible for a number of miscarriages and stillbirths, however this is unconfirmed. 

There is currently no cure for Lethal Infantile Mitochondrial Myopathy. Treatment will focus on reducing discomfort that occurs as a result of the symptoms and managing any life-threatening risks that may arise. 

Prognosis is poor and children with the disorder are not expected to live past the first few months of their life. Of the reported cases, two of the children did not live beyond a few days, and the third child lived to 4 months of age. 

There is very little information on how Lethal Infantile Mitochondrial Myopathy occurs in infants. 

It has been suggested that the disorder is inherited in what is called a mitochondrial pattern. Information about the mitochondria is always inherited from your mother. This means that a female with the condition will pass it on to any children that she has. A male with the condition will never pass it on to his children because he does not provide the genetic information for mitochondria. 

However, Lethal Infantile Mitochondrial Myopathy is unusual because the mother may not show any signs of the disorder, even if it is in her genes. This suggests that it is caused by a random mutation in your genes. 

If you would like more guidance on whether your family should be tested, speak to your medical team. 

References are available on request. Please contact us on 0800 652 3181 or by emailing contact@metabolicsupport.org.

Please note calls to 0800 numbers are free from UK landlines and mobiles. Calls from business lines may be charged – please check with your provider.

This information about metabolic diseases is provided by Metabolic Support UK and is intended for educational purposes only. It should not be used for diagnostic or treatment purposes.

Should you require more detailed information please contact Metabolic Support UK by email (contact@metabolicsupport.org) or by telephone ( 0800 652 3181). For specific medical information regarding a disorder or individual please contact your GP or Paediatrician. Metabolic Support UK accepts no responsibility for any errors or omissions nor does Metabolic Support UK assume any liability of any kind for the content of any information contained within this summary or any use that you may make of it.