Background: The current study tried to evaluate the quality of life (QOL) of phenylketonuria (PKU) patients residing in Tehran, Iran and it also tried to determine the average quality of life of patients. Various aspects of QOL have been analyzed depending on gender, age, and educational levels of the subjects.

Methods: The sample of the study consisted of late-diagnosed PKU patients who were referred to Mofid Children’s Medical Center as well as to Ali-Asghar Hospitals in order to receive metabolic diets on a one year period starting from spring 2013 to spring 2014. Due to the limited study population, subjects were selected via census, therefore 82 patients were enrolled. The research material consisted of the Persian edition of World Health Organization Quality of Life questionnaire (WHOQOL-BREF), designed to examine physical, mental, social and environmental health. The data was gathered on two levels-descriptive and inferential- by using the SPSS software, V.20.

Results: Results indicated that the low quality of life in the late-diagnosed patients suffering from PKU, with mental, physical, social, and environmental aspects, was below the average. Still, even if it was not gender dependent, QOL was greatly influenced by the educational level of the patients. Moreover, it was discovered that the mental health of the patients above 40 years old was significantly lower than the other age groups.

Conclusions: According to the findings of this study, it was recommended that special attention should be given to the improvement of the social and mental health of PKU patients.