RAI1 and obesity due to melanocortin 4 receptor deficiency: The RAI1 gene is known as the primary gene for Smith-Magenis syndrome (SMS, MIM 182290) (prevalence 1:25,000), which is characterized by variable intellectual disability including speech and motor delay, behavioral abnormalities like self-injurious and/or aggressive behavior, sleep disturbance, particular craniofacial and skeletal abnormalities, obesity, hearing loss, hoarse voice and other characteristic traits.