Soomes harva esinev, mujal üsna tavaline kaasasündinud ensümaalne häire (fenüülalaniin­hüdroksülaasi vaegus), mille korral fenüülalaniini ja selle ainevahetusproduktide kogunemine organismis viib ravimatu raskekujulise oligofreeniani, fenüülalaniini ainevahetuse pärilik, aju kahjustav häire, inherited autosomal recessive genetic disorder due to mutations in the PAH gene which results in low levels of the enzyme phenylalanine hydroxylase (PAH), which in turn results in decreased metabolism of phenylalanine (an amino acid), an inherited metabolic disorder caused by an enzyme deficiency resulting in accumulation of phenylalanine and its metabolites in the blood causing usually severe mental retardation and seizures unless phenylalanine is restricted from the diet beginning at birth