Which genetic syndrome is the leading genetic cause of obesity?

• A. Lesch-Nyhan syndrome
• B. Cerebral palsy
• C. Prader-Willi syndrome
• D. Down syndrome

Answer: (C)

Prader-Willi syndrome is the condition where obesity becomes a prominent, defining feature due to disruption of hypothalamic signals that regulate appetite. In this syndrome, the paternal genes in the 15q11-q13 region are lost or silenced, most commonly from a paternal chromosome deletion or maternal uniparental disomy. That genetic change leads to insatiable hyperphagia starting in childhood, so without rigorous environmental control and treatment, obesity tends to develop.

Understanding the pattern helps: infants with Prader-Willi often have low muscle tone and feeding difficulties, but then children develop a relentless desire to eat and can become severely overweight. Additional signs include short stature, hypogonadism, and some learning or behavioral challenges, which together point toward this specific genetic syndrome.

The other conditions listed don’t center on obesity as a defining feature. Lesch-Nyhan involves metabolic and neurological problems with self-injury; cerebral palsy is a motor disability from early brain injury; Down syndrome carries an increased obesity risk but isn’t a genetic cause of obesity in the same way Prader-Willi is.