This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetic and genetic disorders, Subject name: Pediatrics
A child with a small head, minor anomalies of the face including a thin upper lip, growth delay, and developmental disability can have all of the following,except 
Select and explain. 
A. A chromosomal syndrome, B. A teratogenic syndrome, C. A mendelian syndrome, D. A polygenic syndrome
D: A polygenic syndrome
Answer: D: A polygenic syndrome 
Explanation: The features given can occur as a pa of a chromosomal / teratogenic / mendelian syndrome. Polygenic inheritance is the answer of exclusion. In a polygenic inheritance, multiple genes are involved in the phenotypic expression. Some examples of polygenic inheritance are hypeension and diabetes. Reference: GHAI Essential pediatrics, 8th edition