During a 20-week anomaly scan, ultrasound shows bilateral choroid plexus cysts (CPCs), clenched fists with overlapping fingers, and a 'strawberry-shaped' calvarium. Which chromosomal abnormality is most strongly associated with this triad?

• A Trisomy 21 (Down syndrome)
• B Turner syndrome (45,X)
• C Trisomy 13 (Patau syndrome)
• D Trisomy 18 (Edwards syndrome) ✓

Explanation

Trisomy 18 (Edwards syndrome) has a classic ultrasound triad of bilateral choroid plexus cysts, clenched fists with overlapping index fingers (over the 3rd/4th fingers), and a strawberry-shaped calvarium (flat occiput, bifrontal narrowing). Other features include cardiac defects (VSD), single umbilical artery, IUGR, and rocker-bottom feet. CPCs alone are a soft marker (2–3% associated with trisomy 18), but the full triad makes trisomy 18 the strongest association. Trisomy 21 shows nuchal fold thickening, short humerus, and echogenic bowel. Trisomy 13 shows holoprosencephaly and cyclopia.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.