A child brought with seizures and impairment of development is diagnosed having phenylketonuria. What is the initial line of treatment in this child?

Phenylketonuria: It is an autosomal recessive metabolic disorder, where the level of hepatic enzyme phenylalanine hydroxylase is low, therefore phenylalanine cannot be conveed to tyrosine. Phenylalanine accumulates in the blood, cerebrospinal fluid and tissues. Accessory metabolic pathways sta operating which conve phenylalanine to phenylpyruvic acid, phenyl-lactic acid and o-hydroxyphenyl-acetic acid. Restriction of phenylalanine in the diet is the mainstay of treatment of phenylketonuria. Ref: Essential Pediatrics by O.P. Ghai, 6th edition, Page 609.