A 3-year-old presents with severe intellectual disability, absent speech, inappropriate laughter, seizures, and ataxic gait. EEG shows characteristic high-amplitude delta waves with superimposed spike discharges. Genetic testing reveals a deletion of the maternal chromosome 15q11-q13. The diagnosis is:

• A Prader-Willi syndrome
• B Rett syndrome
• C Fragile X syndrome
• D Angelman syndrome ✓

Explanation

Angelman syndrome results from loss of function of the maternally-imprinted UBE3A gene, most commonly due to deletion of maternal 15q11-q13 (70%), or paternal uniparental disomy, or imprinting defects. Classic features: severe intellectual disability, absent/minimal speech (speech delayed beyond all motor milestones), 'happy puppet' appearance with inappropriate laughter, ataxia, and epilepsy. Prader-Willi syndrome results from paternal 15q11-q13 deletion and presents with hypotonia, hyperphagia, and hypogonadism.

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.