Clinical and Paraclinical Characteristics of Non-Classic Phenylketonuria

OBJECTIVE: Phenylketonuria (PKU) is one of the most common inherited metabolic diseases, which is classified into classic and non-classic types. It is estimated that 2% of children with PKU develop a severe and progressive neurological disease, called non-classic (malignant) PKU. This study aimed to demonstrate the clinical features, laboratory findings, and diagnostic/therapeutic characteristics of non-classic PKU patients referred to a tertiary referral center for children in Tehran, Iran. MATERIALS & METHODS: In this study, background information, such as gender and age, clinical manifestations, laboratory findings, and response rate to conventional treatment, was investigated in patients with non-classic PKU, who were referred to Mofid Children’s Hospital in Tehran, Iran, through neonatal screening. RESULTS: Twenty patients with a diagnosis of non-classic PKU were included in this study. The mean age of the patients was 6.00±2.81 years (range: 2-12 years), and 45.0% were male. In patients with a late diagnosis, the most common presentations were motor developmental delay (15.0%), skin and cutaneous manifestations (15.0%), seizure (5.0%), and restlessness (5.0%). The overall response rate to treatment was 85.0%. Factors that predict good response to treatment included female gender, higher neopterin level, and lower age at diagnosis and management. CONCLUSION: In conclusion, about half of patients with non-classic PKU remain asymptomatic, which is due to early diagnosis via neonatal screening. Also, higher age at diagnosis and treatment, besides low neopterin levels, may be useful as prognostic factors.