This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cataract, Subject name: Ophthalmology
Not a cause of pre-senile cataract: 
Select and explain. 
A. Diabetes mellitus, B. Myotonic dystrophy, C. Posterior polar cataract, D. Marfan's syndrome
D: Marfan's syndrome
Answer: D: Marfan's syndrome 
Explanation: Marfan's syndrome is not a cause of pre-senile cataract. Pre-senile cataract Cataract onset before 50 years of age. Causes Diabetes Mellitus. Atopic dermatitis. Steroid Induced cataract. Posterior polar cataract. Myotonic dystrophy.