Patient with Phenylketonuria and Intellectual Disability-Problem Not Always Caused Exclusively by Insufficient Metabolic Control (Coexistence of PKU and Alazami Syndrome).

The authors present a case report of a boy with a classical form of phenylketonuria and Alazami syndrome. The inborn error of phenylalanine metabolism was diagnosed in the neonatal period based on population new-born screening. Despite early implementation of a low-phenylalanine diet and good biochemical control, the patient developed behavioural disorders and intellectual disability. He also presented with dysmorphic features. After long and extensive attempts to establish the genetic cause of this unusual phenotype, finally, at the age of 16 the boy was diagnosed with Alazami syndrome based on whole exome sequencing. The authors discussed the problem of neuropsychological disorders in patients with phenylketonuria and described typical clinical symptoms of Alazami syndrome. It was emphasized that the presence of one monogenic disease does not exclude the coexistence of another one.