Phenylketonuria is caused by decreased or absent phenylalanine hydroxylase, which causes phenylalanine to build up in the tissues and cause brain damage. It presents with musty urine and vomiting and can lead to seizures if not treated appropriately. The patient should be made NPO and IV fluids initiated in order to halt further build-up of phenylalanine. Once that occurs, the state lab can be contacted for newborn screen results. A lactose-free formula and breastfeeding are not appropriate interventions when PKU is suspected – these interventions will lead to further decompensation.