My Grandson Was 5 In March He Was Diagnosed Wit

my grandson was 5 in march he was diagnosed wit leigh disease when he was about 9 months old hes doin good but he cant stand or walk can only sit for a second unaided has no cordination so ders very little tings he can play wit has poor muscle tone no speech an is peg fed cant have anything by mouth.doctors say he has 99% of de disease. his mother my daughter was only diagnosed through blood tests aftr her son was diagnosed..de say she has 74 % of it. she was never very sick but always suffered vomiting bad headackes and dizzy spells .how did shs get into her twenties without any problems anytime she went to doctors b4 all this de said she was fine .