WEST-E Special Education Practice Test

What is the main outcome of phenylketonuria (PKU) if untreated?

1. Visual impairments

2. Intellectual disability

3. Hearing loss

4. Loss of motor skills

The correct answer is: Intellectual disability

The primary outcome of untreated phenylketonuria (PKU) is intellectual disability. PKU is a metabolic disorder caused by a deficiency in the enzyme needed to process phenylalanine, an amino acid found in many protein-containing foods. When individuals with this condition consume phenylalanine, their bodies cannot break it down effectively, leading to toxic levels in the bloodstream. If left untreated—typically through dietary management—these elevated levels can severely impact brain development, resulting in cognitive impairments and intellectual disability over time. Early detection through newborn screening allows for dietary restrictions that limit phenylalanine, which can prevent these detrimental effects on cognitive function. Thus, the significant risk posed by untreated PKU underscores the importance of early intervention and ongoing management of the condition to preserve intellectual capabilities.