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: Pediatrics
Which is not true about Fragile X syndrome? 
Select and explain. 
A. Large testis, B. Pigmented nevi, C. Large ear present, D. No large nose
B: Pigmented nevi
Answer: B: Pigmented nevi 
Explanation: Fragile - X syndrome 

Fragile - X syndrome is the prototype of diseases in which the mutation is characterized by a long repeating sequence of three nucleotides.
In fragile X syndrome, trinucleotide repeat mutation involves CGG on the non-coding region.

Clinical features of fragile - X syndrome

Mental retardation  
Long face with large mandible
Hyperextensible joint 
Mitral valve prolapse
Large everted ears
Large testis (macroorchidism) 
High arched palate       
Fragile X syndrome is the second most common cause of mental retardation, after Downs syndrome.