A neonate is born with hypotonia, feeding difficulty, almond-shaped eyes, small hands and feet, and cryptorchidism. He later develops hyperphagia and obesity. The chromosomal mechanism responsible for this condition is:
- A Paternal deletion of chromosome 15q11–13 ✓
- B Trisomy 15
- C Maternal uniparental disomy of chromosome 15 (paternal genes absent)
- D Microdeletion of chromosome 22q11.2
Correct answer: A. Paternal deletion of chromosome 15q11–13
Explanation
Prader-Willi syndrome (PWS) is caused by absence of paternally imprinted genes on chromosome 15q11–13, most commonly (70%) through paternal deletion of this region. Maternal uniparental disomy (mUPD) of chromosome 15 accounts for ~25% of PWS cases. In contrast, Angelman syndrome results from absence of maternally expressed genes at the same locus (maternal deletion or paternal UPD). The clinical features of neonatal hypotonia, hypogonadism progressing to childhood hyperphagia and obesity are classic for PWS. Chromosome 22q11.2 deletion causes DiGeorge/velocardiofacial syndrome.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.