What should be included in the teaching plan for parents of an infant diagnosed with phenylketonuria (PKU)?
Correct Answer: A
Rationale: The correct answer is A: 'Mental retardation occurs if PKU is untreated.' Phenylketonuria (PKU) is a metabolic disorder that, if left untreated with dietary management, can lead to severe mental retardation due to the accumulation of phenylalanine. It is crucial for parents to understand the potential consequences of untreated PKU to emphasize the importance of early and consistent treatment. Choice B is incorrect because testing for PKU is typically done through newborn screening shortly after birth, not immediately. Choice C is incorrect as treatment for PKU primarily involves strict dietary management that restricts phenylalanine intake, not lifelong medications. Choice D is incorrect as PKU is inherited in an autosomal recessive pattern, meaning that both parents must pass on a mutated gene for the disorder to manifest.