Which genetic disorder requires newborn screening specimens to be drawn shortly after birth?

Phenylketonuria (PKU) is a genetic disorder that specifically requires early detection through newborn screening. PKU is a metabolic condition caused by a deficiency in the enzyme phenylalanine hydroxylase, which leads to the accumulation of phenylalanine in the body. If left untreated, this buildup can cause severe intellectual disability and other neurological problems.

Newborn screening for PKU typically involves a blood sample, often collected through a heel prick, within the first few days of life, ideally within the first 48 to 72 hours. This early screening is critical because, with prompt diagnosis and intervention through dietary management, individuals can lead healthy lives and prevent the adverse effects associated with the disorder.

In contrast, while sickle cell disease and cystic fibrosis also require newborn screening, their protocols may allow for slight delays beyond the initial days after birth. Down syndrome, on the other hand, is primarily diagnosed through genetic testing and not through metabolic screening, making it less relevant for immediate specimen collection shortly after birth.