Hi, I’ve got mild/moderate PKU, but was diagnosed with hyperphe as an infant in the early ’70s. To try to put your mind a bit more at ease, let me tell you a bit about my experience. In the ’70s, it was standard practice to have kids with classic PKU on the diet and formula only until age 6. Having hyperphe, I was on the formula only until age 3. In the ’80s, they discovered that this was a bad idea, and began recommending diet-for-life. However, as my doctors had told us a decade earlier that I wouldn’t need further treatment, we never knew about the change in treatment protocol. I learned about the recommendation of diet-for-life in my early 30s, and after being off-diet for 29 years, contacted a geneticist and dietician and went back on-diet. Despite being off-diet all that time, I have never had any negative effects. I live a completely normal life (aside from the diet and formula), I’m married, have a master’s degree, and function normally in society. That said, EVERY case is different and you need to follow your doctor’s recommendations regarding your son’s care. If they recommend he stays on the diet, KEEP him on the diet. There is currently a debate, apparently, on whether those with hyperphe, like your son, need to be kept on-diet. As a child, he likely will be, to ensure that his development is as healthy as possible. As an adult, he may be able to relax or stop the diet, depending on how high his levels are untreated. As for now, 3.7 is a good, healthy phe level. If you keep him near that, he should do well. The doc will determine what foods to try him on based on his/her experiences with other PKU/hyperphe kids and your son’s tolerance for higher dietary phe. How much dietary phe he can have will be determined the same way, based on how he responds to higher phe intake. The pill that will likely be introduced soon (Kuvan) does not block phe. What it does (trying to keep it fairly simple) is to help the body’s residual ability to metabolize phe to work better. Which is why it won’t work in many people with classic PKU, as they have little to no ability to metabolize any phe, whereas someone like myself and possibly your son, who still have some ability to process the phe, could benefit. Hope this helps.