What is the primary result of a rare recessive gene syndrome associated with PKU?

Phenylketonuria (PKU) is a genetic disorder resulting from a deficiency in the enzyme phenylalanine hydroxylase, which is responsible for metabolizing the amino acid phenylalanine. When an individual has two copies of the recessive gene that causes PKU, they are unable to properly break down phenylalanine. If this condition is not managed through dietary restrictions, toxic levels of phenylalanine accumulate in the body, particularly affecting brain development.

The primary result of untreated PKU is profound intellectual disability, which occurs due to the neurotoxic effects of elevated phenylalanine levels. Early diagnosis and intervention, such as a strict low-phenylalanine diet initiated shortly after birth, can prevent this severe cognitive impairment. Therefore, the association of PKU with profound intellectual disability is a well-established outcome when the condition is not effectively managed.

Other results, such as behavioral dysregulation or developmental delays, while they may occur, are not the defining or primary outcomes of this syndrome. Instead, it is the profound intellectual disability that stands out as the most critical consequence of a failure to adequately treat this genetic disorder.