Prader-Willi syndrome is characterized by hyperphagia, severe obesity, and intellectual disability. None of the pother disorders listed are characterized by hyperphagia to the point of Prader-willi. [FA2020 p58]

• Angelman is the other disorder of imprinting (like Prader-Willi) except it is characterized by seizures, ataxia, severe intellectual disability, and inappropriate laughter.
• Down syndrome is characterized by intellectual disability, single palmar crease, duodenal atresia and heart defects are common [FA2020 p63]
• Fragile X syndrome is the most common inherited cause of intellectual disability and is characterized by autism, long face with large jaw and everted ears, mitral valve prolapse, and hypermobile joints [FA2020 p62]
• Williams syndome is a neurodevelopmental disorder of mild intellectual disability, outgoing personality, hypercalcemia, and elvin face (Will Ferrel in Elf, FA2020 p64)