This is a disorder caused by the deficiency of phenylalanine hydroxylase hence the patient is unable to digest phenylalanine ^[1]. In severe cases, a build up of phenylalanine in the body can lead to brain damage and mental retardation. This condition can also cause eczema and pigment defects resulting in lighter tone of skin ^[2]. Sufferers of this disorder should be placed on a low phenylalanine diet to minimise effects of the condition ^[3].

References

1. ↑ . Stryer,L., Jeremy M. Berg and John L. Tymoczko Biochemistry, 5th Ed.
2. ↑ Paul, D. A double-edged sword. Nature 405, 515 (2000) doi:10.1038/35014676
3. ↑ Hartl, D. L. and Jones, E. W. (2006) Essential genetics : a genomics perspective.4th ed.