Karl Swaine (9) with his brother, Cillian (4), and his mother, Sharon, at home in Lucan. Karl has Hunter syndrome and is being treated in Temple Street Children’s Hospital, Dublin. Photograph: Brenda Fitzsimons.

“All I kept thinking was ‘is my son going to die when he is 11?’.” Sharon Byrne remembers the fear she felt when she heard her son’s diagnosis of a ra(...)