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: Skin
All are true about Langerhans' histocytosis except? 
Select and explain. 
A. Common before 3 years of age, B. Letterer Siwe disease is systemic manifestation, C. Radio sensitive, D. Testis is commonly involved
D: Testis is commonly involved
Answer: D: Testis is commonly involved 
Explanation: D. i.e. Testis is commonly invoved