Significant weight loss with cognitive and communication limitations in an adolescent

Mark is a 17-year-old adolescent with an unknown dysmorphic syndrome associated with intellectual disability. His food intake was limited for at least 3 months. He refused all foods, while he lost 12 pounds in 9 months. His mother said that he has been in a good mood and performing at his baseline level in school. Mark has a limited expressive verbal capacity; he uses some single words, he can express pain, but he has minimal understanding of conversation. He has an appointment at the primary care pediatric clinic for a weight check.