This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Anatomy
Regression of milestones is seen in all except 
Select and explain. 
A. Childhood disintegrative disorder, B. Retts syndrome, C. Landau kleffner syndrome, D. Klein levin syndrome
D: Klein levin syndrome
Answer: D: Klein levin syndrome 
Explanation: Regression refers to loss of learned brain functions and is a symptom characteristic choice 1,2,3