American Board of Psychiatry and Neurology (ABPN) Practice Exam

Prader-Willi syndrome is characterized by a combination of developmental delays, hypotonia (decreased muscle tone), and a spectrum of intellectual disabilities. In particular, children with Prader-Willi syndrome often display significant feeding problems during infancy due to hypotonia, leading to issues with weight gain and growth in early childhood. As they grow, they might exhibit behaviors and physical characteristics associated with the condition, such as obesity, learning disabilities, and social challenges.

The association of developmental delay and hypotonia is particularly prominent in Prader-Willi syndrome, making it a likely diagnosis for a child presenting with these symptoms. In contrast, while the other syndromes listed can also involve developmental delays, their specific features diverge from hypotonia and developmental delay as defining markers. For instance, Trisomy 21, known as Down syndrome, includes hypotonia but also presents with distinct facial features and additional medical concerns that are not strictly developmental delays alone. Williams' syndrome and Fragile X syndrome have different hallmark traits and typically involve different behavioral and intellectual profiles. Thus, the combined symptoms of developmental delay and hypotonia align most closely with Prader-Willi syndrome.