A pregnant woman with untreated classic phenylketonuria has plasma phenylalanine persistently above 1200 micromol/L despite being heterozygous-normal herself. Which fetal outcome is most directly attributable to maternal hyperphenylalaninemia?
- A Microcephaly, congenital heart defects, and intellectual disability even if the fetus lacks PAH mutation ✓
- B Congenital cataracts and sensorineural deafness
- C Neonatal hypoglycemia and hepatomegaly resolving within one week
- D Isolated growth restriction with normal neurodevelopment
Correct answer: A. Microcephaly, congenital heart defects, and intellectual disability even if the fetus lacks PAH mutation
Explanation
Maternal PKU syndrome occurs because phenylalanine crosses the placenta freely and is a teratogen. Affected offspring show microcephaly, intellectual disability, congenital heart disease, and low birth weight regardless of the child's own genotype. This is why strict preconception and prenatal phenylalanine control below 360 micromol/L is advised. Cataracts point to galactosemia, not maternal PKU.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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