Judges at the European Court of Human Rights have ruled that the treatment Charlie Gard is receiving should be extended until 19 July, to give them time to consider whether they should take on the case.

Charlie was born healthy last August, but after just two months, his health started to deteriorate as he lost weight and strength. He has been in intensive care since last October and doctors have said that he is in the terminal phase of his illness. He was diagnosed with a form of mitochondrial DNA depletion syndrome.

Over the past few months, his parents Connie Yates and Chris Gard have been fighting a bitter legal battle to take their son to the US and allow him to receive experimental treatment.

Charlie is thought to be one of only 16 babies ever to be diagnosed with a mitochondrial DNA depletion syndrome.

What is mitochondrial DNA?

Mitochondria are organelles responsible for creating the energy needed by the cells to function. They are found in the body of every living cell, separated from the nucleus that holds the nuclear DNA – the genetic material inherited both from the mother and the father.

Mitochondria also contain very small amount of DNA. This mitochondrial DNA amounts to 37 genes inherited from our mothers. When mitochondrial DNA is faulty, this can lead to different types of mitochondrial diseases.

What are mitochondrial DNA depletions syndromes?

Mitochondrial DNA depletion syndromes are a genetically and clinically varied group of disorders that are characterised by a severe reduction in mitochondrial DNA content. This leads to impaired energy production in affected tissues and organs.

The conditions are caused by genetic mutations that affect mitochondrial DNA synthesis and replication. There are different types of DNA depletion syndromes, which can lead to muscle weakness before the children reach the age of 2, neurological problems and liver dysfunction.

These are severe disorders with poor prognosis in the majority of cases. So far, no therapy or cure exists to help patients, although nutritional interventions or supplementation can be beneficial for some children.

Furthermore, stem cell transplantation has shown promising results for specific types of mitochondrial DNA depletion syndromes.