What is mitochondrial DNA depletion syndrome and what are the symptoms?
CHARLIE Gard's legal battle reached an end in July 2017, as the tot was moved to a hospice where his life support was withdrawn.
The tot's fight for life touched the world, as he suffered from the rare mitochondrial DNA depletion syndrome.
What is mitochondrial DNA depletion syndrome?
Mitochondrial DNA depletion syndrome (MDS) refers to a group of disorders that cause affected tissues to suffer from a significant drop in mitochondrial DNA.
The DNA is found in the mitochondria of cells - an organelle found in most cells in which respiration and energy production occur.
This means sufferers do not get energy to their muscles, kidneys and brain.
MDS causes progressive muscle weakness and brain damage.
The condition is rare.
MDS is almost always fatal in babies and young children, although some sufferers have made it into their teenage years.
There's currently no cure, but some treatments have shown a reduction in symptoms.
One of these is Nucleoside bypass therapy.
What are the symptoms of mitochondrial DNA depletion syndrome?
Symptoms usually develop before a baby is one year old.
The disease can cause the slowing down of thoughts and a reduction in physical movement, hearing impairment and seizures.
Other symptoms include problems with blood glucose levels, persistent vomiting and a failure to thrive when babies are in their first year of life.
The NHS says a lack of energy is a common symptom on the outside, but MDS can cause "any symptom, in any organ, with any degree of severity, at any age".
However, many of the symptoms are common to other diseases so MDS can often be hard to diagnose.
What happened to Charlie Gard?
Charlie was born a "perfectly healthy baby" in August 4, 2016.
But a month after his birth, his parents Connie Yates and Chris Gard noticed he was struggling to lift his head and couldn't support himself as well as other babies around the same age.
Medics at Great Ormond Street diagnosed him with the inherited condition infantile onset encephalomyopathy mitochondrial DNA depletion syndrome (MDDS).
This meant Charlie suffered from muscle weakness and brain damage as both of his parents Connie and Chris were unknowingly carrying the faulty gene.
Charlie passed away on Friday, July 28, 2017.
Doctors at Great Ormond Street Hospital had said Charlie should be allowed to die in dignity.
They applied for permission to have his ventilator switched off.
But his parents were fighting this decision – raising more than £1.3 million to pay for pioneering treatment in the US.
They ended their fight because “time has run out”.
What is nucleoside bypass therapy and does it work?
Charlie's parents were fighting for him to be taken to the US after a doctor in the States offered them nucleoside bypass therapy.
In theory, it could have seen Charlie’s mitochondrial DNA synthesise again by giving him the naturally occurring compounds his body isn’t able to produce.
It is an experimental new treatment taken as an oral medication.
The drug has not even been tested on mice for Mitochondrial DNA depletion syndrome.
However, doctors say it has been tested on mice and patients with a different mitchondrial condition and has brought about “dramatic clinical improvements”.
The family said they had seven specialist doctors - including one from England - supporting their calls for Charlie to be given the treatment.
A US expert said 18 people have been treated with nucleoside bypass therapy. But he added that none of them were in a condition as severe as Charlie’s.
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Have other children been treated using nucleoside medication?
Art Estopinan's son, Art Jr, suffers another form of mitochondrial depletion called TK2 - a "cousin" disease to Charlie's.
Charlie's condition is more serious as it means his brain is affected as well as his muscles.
Five years ago, Art Jr appeared to be facing death when he became the first human to be given nucleoside medication.
Art said his son was given a "new lease of life" by the drug and can now stand with the help of a brace and say a small number of words.