A nurse is assessing a 3-month-old infant who was recently diagnosed with phenylketonuria (PKU). Which assessment finding would be most concerning and require immediate intervention?
1Mild developmental delay in motor skills
2Musty or mousy odor from the infant's urine and skin✓ 정답
3Fair skin and light-colored hair
4Decreased appetite during feeding times
해설
Musty or mousy odor indicates elevated phenylalanine levels in PKU, requiring immediate dietary intervention to prevent irreversible neurological damage. Other findings are typical of PKU but less urgent.
Clinical Judgment
This question assesses the ability to identify the most urgent danger signal in the evaluation of a child with phenylketonuria (PKU). The key is to establish clinical priorities. While all options can be associated with PKU, a musty/mousy odor is a Notify HCP! sign that directly indicates active, ongoing metabolic toxicity and the risk of immediate neurological damage. It signifies that dietary control is insufficient or has not been initiated, requiring immediate intervention to prevent intellectual disability. The other options may be characteristics of PKU or long-term consequences, but this specific odor represents a current biochemical crisis.
Memory Tip: Mousy odor = Metabolic emergency. The "M" smell in PKU means "Must Act Now."
KR vs US: Both Korea and the US diagnose PKU early through newborn screening. The core management principle (low-phenylalanine diet) is the same, but in the US, there may be differences in insurance coverage and access to special formulas and low-protein foods. The nurse's role in education and monitoring is equally important.
임상 시나리오
Clinical Practice Guide
The goal of PKU management is to maintain blood phenylalanine levels within the therapeutic range of 2-6 mg/dL (or 120-360 µmol/L). This is achieved through special formulas (e.g., Lofenalac, Phenyl-Free), strictly limited natural protein intake, and phenylalanine-free medical foods. Regular blood tests are essential.
Caution: In SATA (Select All That Apply) questions asking for "all symptoms" of PKU, while "mild motor developmental delay" or "light skin/hair" can be associated with PKU, they do not appear immediately in the newborn/early infant period. "Musty odor" and "poor feeding" are more urgent signs. The presence of "phenylketones" in urine is also an important laboratory finding, but the odor is a more direct clinical signal.
핵심 개념
Phenylketonuria — An autosomal recessive inherited metabolic disorder caused by a congenital deficiency of phenylalanine hydroxylase, the enzyme that converts phenylalanine to tyrosine. If left untreated, it causes severe intellectual disability.
Phenylalanine — One of the essential amino acids. In patients with PKU, this amino acid cannot be metabolized, so it accumulates in the blood and causes neurotoxicity. It must be strictly restricted in the diet.
Musty/Mousy Odor — Characteristic odor from the urine, sweat, and skin of PKU patients. It occurs due to the accumulation of phenylalanine metabolites such as phenylpyruvic acid, phenyllactic acid, and phenylacetic acid, and is a clinical indicator of high phenylalanine levels.
Phenylalanine-Restricted Diet — Core treatment for PKU management. It is a lifelong dietary therapy that uses special formula (low in phenylalanine) and strictly limits natural protein intake to maintain blood phenylalanine levels within a safe range.
Newborn Screening — A blood test performed within the first few days after birth as part of a program to detect several congenital metabolic abnormalities and diseases, including PKU, at an early stage. It enables early diagnosis and initiation of treatment.