Phenylalanine hydroxylase (PAH) deficiency is a rare disease caused by an inborn error of metabolism. If left untreated, PAH deficiency results in progressive, irreversible neurological impairment during infancy and early childhood.~This study is designed to collect information about important PKU-related symptoms and tests to characterize the natural history of PKU due to PAH deficiency in a selected sample of adults. No new investigational treatment will be administered to participating patients.
The objective of this study is to characterize the natural history of phenylketonuria (PKU) due to phenylalanine hydroxylase (PAH) deficiency in adults through prospective collection of clinical, cognitive, and quality of life assessments.