As far as I know there are two units for measuring phe levels. One is mg/dl and the other is umol/l. If your sons levels are 240umol/l then in mg/dl their levels would be 4mg/dl. Phe levels are suppose to be between 2-6mg/dl (or 120-360umol/l), so your sons levels are great!! People are born with PKU throughout the world, but because PKU occurs more in people who are irish or caucasion some places have a higher population of Phenylketonurics.