A 2-week-old neonate with suspected Down's syndrome exhibits phenotypic features including:

A 2-week-old neonate with suspected Down's syndrome exhibits phenotypic features including:

• A. Large ears and small mouth, short fingers, and jaundice
• B. Small ears, short neck, and hypotonia
• C. Flat nasal bridge and normocephaly
• D. Protuberant tongue, microcephaly, and jaundice

Answer: (B)

Neonatal hypotonia is a hallmark finding in Down syndrome and often appears early, contributing to feeding challenges and delayed motor tone. In newborns with trisomy 21, facial and neck features such as small ears and a short neck are commonly present alongside this low muscle tone. The combination of small ears, short neck, and hypotonia best matches the classic neonatal phenotype of Down syndrome, making it the most characteristic choice. Other options include traits that are less specific or don’t align as well with the typical newborn presentation. For example, large ears and jaundice aren’t characteristic features; a flat nasal bridge can occur but head size described as normocephaly doesn’t emphasize the key hypotonia; a protuberant tongue can occur but microcephaly is not a typical associated finding in Down syndrome.

Neonatal hypotonia is a hallmark finding in Down syndrome and often appears early, contributing to feeding challenges and delayed motor tone. In newborns with trisomy 21, facial and neck features such as small ears and a short neck are commonly present alongside this low muscle tone. The combination of small ears, short neck, and hypotonia best matches the classic neonatal phenotype of Down syndrome, making it the most characteristic choice.

Other options include traits that are less specific or don’t align as well with the typical newborn presentation. For example, large ears and jaundice aren’t characteristic features; a flat nasal bridge can occur but head size described as normocephaly doesn’t emphasize the key hypotonia; a protuberant tongue can occur but microcephaly is not a typical associated finding in Down syndrome.