A 4-year-old boy presents with intellectual disability, supravalvular aortic stenosis, and an unusually friendly, sociable personality. Fluorescence in situ hybridization (FISH) using a probe for the elastin gene on chromosome 7q11.23 is negative. Which diagnosis best explains this phenotype?

• A Angelman syndrome
• B Williams syndrome ✓
• C Smith-Magenis syndrome
• D Noonan syndrome

Explanation

Williams syndrome results from a microdeletion at 7q11.23 encompassing the ELN (elastin) gene. The classic triad includes supravalvular aortic stenosis, intellectual disability with preserved language and music, and a characteristically friendly, 'cocktail party' personality. The absent elastin FISH probe confirms the diagnosis. Smith-Magenis involves chromosome 17p11.2 deletion and features self-injurious behavior, not the described cardiovascular or personality profile.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.