The case of baby Charlie Gard, on life support in a British hospital with a rare genetic condition, has put a spotlight on experimental treatment called nucleoside drug therapy. His parents want him to travel to the US for treatment, but his doctors say this would not improve his quality of life and he should be allowed to die.

A family in the US state of Maryland told the BBC's Aleem Maqbool what happened to their son who also has a mitochondrial disorder, although doctors caution that Charlie's condition could be more severe.