A newborn boy presents with characteristic facial features including upslanting palpebral fissures, epicanthic folds, and a flat nasal bridge. On hand examination, the midwife identifies the structure marked **A** in the diagram. Which of the following statements about this finding is most accurate in the context of Down syndrome screening?

Question

Accepted Answer

A. It is present in approximately 45% of children with Down syndrome and 1–2% of the general population, making it a useful soft marker for aneuploidy screening. ## Why option 1 is right

The single transverse palmar crease (simian line) marked **A** is present in approximately 45% of children with Down syndrome compared to only 1–2% of the general population. This makes it a valuable soft marker for Down syndrome screening in the neonatal period. While not diagnostic on its own, its presence in conjunction with other clinical features (facial dysmorphism, hypotonia, cardiac findings) significantly raises suspicion for trisomy 21 and warrants further investigation including karyotyping and FISH analysis. According to Bull MJ et al. (Pediatrics 2011), this crease is one of the recognized hand findings in Down syndrome neonates and should prompt comprehensive evaluation.

## Why each distractor is wrong

- **Option 2**: The single palmar crease is not pathognomonic for Down syndrome. While it is a well-recognized soft marker, it can occur in other chromosomal abnormalities (such as Edwards syndrome) and even in unaffected individuals. Its presence alone does not confirm trisomy 21.
- **Option 3**: The single palmar crease is a distinct finding from hypoplasia of the middle phalanx of the fifth digit (clinodactyly). While both can occur in Down syndrome, they are separate anatomical features. The crease itself does not directly cause intellectual disability but is associated with the underlying chromosomal abnormality.
- **Option 4**: The single transverse palmar crease is not a normal variant in neonates. Its presence, especially in combination with other dysmorphic features, warrants immediate investigation and should never be dismissed as benign.

**High-Yield:** Single transverse palmar crease (simian line) is present in ~45% of Down syndrome but only ~1–2% of general population — a key soft marker that should trigger karyotyping when seen with other features.

[cite: Bull MJ et al. Health supervision for children with Down syndrome. Pediatrics 2011;128(2):393-406.]

Answer

B. It is caused by hypoplasia of the middle phalanx of the fifth digit and indicates severe intellectual disability

Answer

C. It is pathognomonic for Down syndrome and is absent in all other chromosomal abnormalities

Answer

D. It is a normal variant in neonates and requires no further investigation or follow-up

Explanation

Why option 1 is right

Why each distractor is wrong

Practice similar questions

Join our NEET PG community