Lethal Infantile Mitochondrial Myopathy

What else is it called?

  • LIMD 
  • LIMM 
  • Lethal infantile mitochondrial disease 

Get in touch

Contact our caring team on 08452 412 173 for help and support. Our phone lines open 10am-4pm, Monday to Friday.

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What causes it?

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. 

How common is it?

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

What are the signs and symptoms?

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.

How is it diagnosed?

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. 


Can it be treated?

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. 

Do my family need to be tested?

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. 

Relevant Organisations


References are available on request. Please contact Helen Morris by phoning 0845 241 2173 or emailing helen@metabolicsupportuk.org [Resource Library No: AAP002]. 

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