My 3 year old son suffers from poor weight gain , he was born 3lb 15oz full term, with a sacral dimple, all of his development milestones were late, only started walking last autumn, he has moments where his arms and lower jaw tense up and shake, he weighs only 20lbs now and is really small for a 3 and a half year old. he s seen many doctors and specialists, had x-rays and an mri of his brain and spine , and countless blood tests all came back normal. There are so many syndromes and diseases with these types of symptoms and more that I ve noticed in my son, is there any chance you could point me in the right direction please?