Genetic Screening for Phenylketonuria Among Neonates in Selected Hospitals in Katsina State

Phenylketonuria (PKU) is an autosomal recessive inborn error of metabolism caused by mutations in the PAH gene encoding phenylalanine hydroxylase. Untreated PKU leads to progressive intellectual disability, making early neonatal screening and dietary intervention critical. Newborn screening for PKU is routine in high-income countries but remains largely unavailable in Nigeria. This feasibility study assessed the practicality of tandem mass spectrometry-based PKU screening among neonates in selected hospitals in Katsina State, North West Nigeria. Dried blood spot (DBS) samples were collected from 500 neonates within the first 48 hours of birth at three hospitals. Samples were analysed for phenylalanine levels using tandem mass spectrometry. Samples with phenylalanine above the cutoff of 120 micromoles per litre were recalled for confirmation and PAH gene sequencing. Three neonates had elevated phenylalanine levels on initial screening, of whom one was confirmed as classic PKU on repeat testing. PAH gene sequencing identified the causative pathogenic variant. This study demonstrates the feasibility of DBS-based PKU screening in Katsina State and advocates for its expansion within a national newborn screening programme. Keywords: phenylketonuria, newborn screening, PAH gene, dried blood spot, Katsina State