PAH and Intellectual disability: PKU is caused by pathogenic variants in the phenylalanine hydroxylase (PAH) gene, resulting in reduced conversion of the essential amino acid phenylalanine (Phe) into tyrosine.1 While several pharmacologic therapies are available,1, 2 medical nutrition therapy (MNT) is the primary treatment for PKU, and requires restricting dietary Phe to individual Phe tolerance and supplementing with Phe‐free medical foods to meet total protein needs.3 Untreated PKU results in severe, permanent intellectual disability.