Question:medium
Which is not a feature of Down syndrome?
Which is not a feature of Down syndrome?
Show Hint
Look for the sign that is not part of the trisomy 21 phenotype.
Updated On: Jun 24, 2026
- Clinodactyly
- Pigmented birth marks
- Hypotonia
- Respiratory tract infections
Show Solution
The Correct Option is B
Solution and Explanation
Step 1: Frame the question. This is a negative-stem item, so I list the true features of trisomy 21 and pick the one that does not belong.
Step 2: Build the true list. Down syndrome shows hypotonia in infancy, fifth-finger clinodactyly and a single palmar crease in the hands, plus a sandal gap in the feet. Frequent respiratory tract infections occur because of associated heart defects, hypotonia and immune differences. Craniofacial clues include epicanthic folds, a flat nasal bridge, protruding tongue and Brushfield spots.
Step 3: Test each option. Clinodactyly, hypotonia and respiratory infections all map onto the real phenotype, so they cannot be the answer.
Step 4: Spot the outlier. Pigmented birth marks (such as cafe-au-lait spots) are not a feature of Down syndrome; they point toward conditions like neurofibromatosis. So the exception is pigmented birth marks.
\[\boxed{\text{Pigmented birth marks}}\]
Step 2: Build the true list. Down syndrome shows hypotonia in infancy, fifth-finger clinodactyly and a single palmar crease in the hands, plus a sandal gap in the feet. Frequent respiratory tract infections occur because of associated heart defects, hypotonia and immune differences. Craniofacial clues include epicanthic folds, a flat nasal bridge, protruding tongue and Brushfield spots.
Step 3: Test each option. Clinodactyly, hypotonia and respiratory infections all map onto the real phenotype, so they cannot be the answer.
Step 4: Spot the outlier. Pigmented birth marks (such as cafe-au-lait spots) are not a feature of Down syndrome; they point toward conditions like neurofibromatosis. So the exception is pigmented birth marks.
\[\boxed{\text{Pigmented birth marks}}\]
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