A judge has told of the nightmare being endured by a couple who have two daughters under five suffering from terminal illnesses.
Mr Justice Williams has paid tribute to the couple after being asked to make decisions about the treatment of the younger child.
He said the younger girl was two and had an extremely rare syndrome which meant that she was likely to die within the next four years.
Her four-year-old sister also had a "terminal condition".
The judge has made decisions relating to the younger girl's treatment after analysing her case at hearing in the Family Division of the High Court in London.
He has revealed details of her case in a ruling just published on a legal website
Mr Justice Williams said he had declared that the little girl should continue to receive "basic intensive care".
But he gave doctors permission to provide palliative care in future if there was "no reasonable expectation" of improvement.
The judge said the child had "defied the odds" and proved to be a fighter.
He said the family could not be identified.
"The little girl whose future I am asked to consider was born in 2015," said Mr Justice Williams in his ruling.
"This is, on any level, a tragic case. (The little girl), it is accepted, suffers from a condition, a syndrome, which is a fatal condition, death usually occurring between two and six years of age.
"It is extremely rare."
He added: "As if that was not enough of a nightmare for (her) and her family, her older sister also has a terminal condition. She is four.
"The parents are both devoted to the girls and have provided outstanding parenting."