This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Psychiatry
X-linked recessive disorder with mental retardation and self mutilation is seen in - 
Select and explain. 
A. Lesch - Nyhan syndrome, B. Fragile X - syndrome, C. Down syndrome, D. All of the above
A: Lesch - Nyhan syndrome
Answer: A: Lesch - Nyhan syndrome 
Explanation: X-linked recessive disorder causing MR :- Lesch - Nyhan syndrome, Hunter's syndrome.
Self-mutilation behavior is seen in Lesch - Nyhan syndrome.