Phenylketonuria (PKU) is a genetic disease that increases blood levels of phenylalanine. Persistent elevations in the concentration of this amino acid in the blood can cause neurological damage which, in its most severe form, is manifested by irreversible mental retardation. The neonatal screening test, carried out on the third to fifth day of life, enables early diagnosis and the start of treatment in good time, with the aim of guaranteeing normal growth and development for the affected child. Dietary treatment, which is very restrictive, is influenced by various factors that produce significant changes in family dynamics and becomes a major challenge for professionals, since purely biological knowledge is not enough to encompass its complexity and how to deal with it. Living with Phenylketonuria sought to emphasise the difficulties of treatment, not only in relation to the restrictive diet, but also in relation to emotional, social, economic and cultural aspects. The study helps to improve understanding of living with the disease in family dynamics, contributing to a more humanised and integrated approach to the treatment of PKU.