Mitochondrial disease??

After 12 months of testing, my 9 year old son has been diagnosed with a mitochondrial disease....possibly Leigh's Syndrome.. After a lot of research, I have discovered that Leigh's syndrome is diagnosed primarily when in infancy and the prognosis is poor and is usually during the first few years of life. . Initially his eyes where the major symptom, along with hypertentsities of the mid brain and brain stem. He has since had chronic and severe vomiting, as well as bowel blockages which require weekly bowel wash outs. He cannot hold or gain weight so is also having enteral nutritional feeds via naso gastric tube, nightly. Could someone please advise