Phenylalanine Restricted Diet Treatment of the Aggressive Behaviours of a Person with Mental Retardation

Abstract

Phenylketonuria is a genetic abnormality that triggers an incapacity to metabolise phenylalanine (Phe), an amino acid present in nutritional proteins. This incapacity leads to an accumulation of Phe and its by-products in the blood and tissues, which drastically compromises the neurological and intellectual development of a person (Pueschel, 1996). Following the establishment of national and state screening programmes (circa 1965), phenylketonuria has ceased to be a cause of mental retardation for the vast majority of persons affected by this incapacity. With the possibility of detection at birth and the immediate introduction of a Phe-restricted diet, development can progress at normal rates (Koch et al., 1996). However, individuals with phenylketonuria who were born before the development of these screening programmes and early interventions have, unfortunately, developed mental retardation. It is clear that the harmful effects of a high Phe blood level during the first years of life are largely irreversible, especially where intellectual development is concerned (Bruhl et al., 1965). However, certain toxic effects manifested in problem behaviours seem to be reversible, even in adults with phenylketonuria who have followed a regular diet throughout their entire lives.