Just in Utah, there have been three more diagnoses of GAMT since Sam's diagnosis in February of 2009. That's a lot when you factor in that Sam was estimated to be the 49th in the world at that time. I also am aware of one case in North Carolina and two in Illinois that have been discovered since then as well. One of the cases in Utah is a second cousin's child who also got lucky and while having some testing done, had a technician decide to run a spectroscopy on a hunch. That hunch saved a little boy's life.
Before PKU was "discovered" and automatically screened for at birth, all those people suffering from a fully treatable disorder were diagnosed as mentally retarded and left un-helped. The same tragedy is happening today to children born with GAMT deficiency. I feel so badly for anyone searching for answers. There are definitely more causes yet to be discovered for developmental delays, but GAMT deficiency is no longer one of them. It has been discovered and is treatable with the best results coming from early treatment. Both Duke University and the University of Utah are working on newborn screening tests that would be able to detect GAMT deficiency from the routine heel pricks babies receive in the hospital, but until then there are bound to be children slipping through the cracks and suffering the consequences for the rest of their lives. The symptoms vary so much from child to child that it's hard to say "look for this one thing".
My advice to anyone whose child is suffering from something un-diagnosed is to push for more testings of all kinds- blood, urine, DNA, MRI with spectroscopy. Don't let a pediatrician or developmental psychologist look at your child only from the outside and slap a give-up label on your child of "delayed" without looking a level deeper for answers. If a thousand children are tested and only one of them gets information that helps in their recovery, isn't it worth it? It's so intimidating to be a parent only armed with "hunches", but even doctors (and MRI technicians) rely on hunches and you know your child better than any doctor.
Just had to put that out there because I wish someone would've said it to me years ago...