Background: Phenylketonuria (PKU) is an inborn error of metabolism that results in decrease 
metabolism of the amino acid phenylalanine (phe). This error causes increased PHE blood 
concentrations and leads to a toxic accumulation in the brain, resulting in cognitive deficiencies, 
emotional disturbance and psychosocial disabilities. Therefore, PKU patients must follow the lifelong 
long protein restricted diet. It is possible that PKU affects PKU patients' quality of life negatively.
Objectives: Aim of the study: We aimed in this study to assess the impact of phenylketonuria on 
quality of life of PKU children. Methods: This study was conducted on children and adolescents 
less than 18 years who were diagnosed as PKU Patient over the period from April to October 2019. 
PKU patients were classified into three group : Group I: children between 2 and 9 years, Group II:
children between 9 and11 years and Group III: adolescents between 12 and 17 years. The three 
groups were subjected to complete history taking, through clinical examination and laboratory 
investigations determining serum phe level . Results: Most of the individuals were male (55.2%) 
with mean age 5.72±3.80 years. Most of them have normal BMI (85.1%), but 14.9% of children were 
overweight .( 65.7% ) were under height, and (34.3%) had normal height. Our results showed that the 
mean phenylalanine level in all studied group was 507.54±279.24, there is no significant differences 
between groups in the mean phenylalanine level (p > 0,05). Conclusion: Phenylketonuria (PKU) 
have more negative effects on quality of life of children and younger individuals.