Charlie Gard is a terminally ill British child whose parents are fighting for the right to take him to the United States for an experimental treatment. His case has gained international attention, including from Pope Francis and U.S. President Donald Trump.

The 11-month-old is being treated at London's Great Ormond Street Hospital, which maintained the experimental treatment was "unjustified" and might cause Charlie more suffering without doing anything to help him. The hospital planned to take the boy off life support, but petitioned for a new court hearing based on evidence from researchers at the Vatican's children's hospital and another facility outside of Britain.

Below is some background on the medical and legal issues behind Charlie's case:

WHAT IS MITOCHONDRIAL DISEASE?

Mitochondrial disease is the umbrella term for a number of rare conditions caused by genetic mutations that result in the failure of mitochondria, specialized compartments within most cells that supply the energy needed to sustain life and support organ function. When mitochondria fail, cells can be injured or die, causing organ systems to shut down. The brain, heart, muscles and lungs are most affected because they need the most energy.

Charlie suffers from a form of the disease known as infantile onset encephalomyopathic mitochondrial DNA depletion syndrome (MDDS.) It is specifically known as the RRM2B mutation of MDDS. There is no known cure.

WHAT IS THE TREATMENT HIS PARENTS WANT FOR CHARLIE?

Doctors in the United States have been experimenting with a treatment known as nucleoside therapy, which has shown success in reducing the symptoms of some types of mitochondrial disease in laboratory mice. The treatment has been administered to a small number of children who have also shown improvement.

However, the treatment has never been used on either mice or humans with the type of mitochondrial disease from which Charlie suffers, according to court documents.

HAS THE NUCLEOSIDE THERAPY BEEN USED BEFORE?

A boy named Arturito Estopinan in Baltimore was the first child to be given deoxynucleotide monophosphate, an experimental treatment that significantly extended the life of mice with the same condition as Arturito, known as TK2-related mitochondrial depletion syndrome.

Art Estopinan, the boy's father, met with Charlie's parents in London to share his experience. He stressed that while the therapy was a treatment, not a cure, his 6-year-old son was "getting stronger every day." Arturito still needs around the clock care. Estopinan and his wife, Olga, have given their lives over to caring for him, hoping that a cure will come one day. The sacrifices keep coming because "we love our son," he said.

"A lot of very smart doctors are unaware of these experimental medications," Estopinan said. "As a father, I cannot sit back and know that my son was saved and not be vocal in support of Charlie Gard receiving these meds."

A CRUEL DISEASE

Sian Harding, Director of the British Heart Foundation Cardiovascular Regenerative Medicine Center at Imperial College, described the difficulty of treating the disease that Charlie has.

"Mitochondrial diseases are cruel because they strike babies and young children, who rapidly deteriorate," Harding said. "It is because there is no cure that the scientific and medical community have concentrated on pre-conception mitochondrial therapy, and it has been an enormous advance that this is now licensed by the government. It allows parents with these mutations to have healthy children, though sadly, cannot help babies already born."

WHY IS IT UP TO THE COURTS AND NOT CHARLIE'S PARENTS?

Parents in Britain do not have the absolute right to make decisions for their children. It is normal for courts to intervene when parents and doctors disagree on the treatment of a child. The rights of the child take primacy, with the courts weighing issues such as whether a child is suffering and how much benefit a proposed treatment might produce.

Professor Dominic Wilkinson, director of medical ethics at the Oxford Uehiro Center for Practical Ethics, said decisions about life-sustaining treatment for a child are "fraught."

"Sadly, reluctantly, doctors and judges are justified in concluding that continuing life support is not always helpful for a child and is in fact doing more harm than good," Wilkinson said. "Providing comfort, avoiding painful and unhelpful medical treatments, supporting the child and family for their remaining time: sometimes that is the best that we can do, and the only ethical course."

Link:

A brief look at the medical issues in the Charlie Gard case - ABC News