This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abnormalities of Development, Subject name: Pediatrics
What is the diagnosis in this child with intellectual disability? 
Select and explain. 
A. Rubinstein Taybi syndrome, B. Seckel syndrome, C. Fragile X syndrome, D. Rett syndrome
C: Fragile X syndrome
Answer: C: Fragile X syndrome 
Explanation: Elongated face with large protruding ears, in a male with intellectual disability suggests a diagnosis of Fragile X syndrome. Fragile X syndrome or Main-Bell syndrome: Due to Gene Mutation in the FMR1 gene on chromosome - X CGG trinucleotide repeats Second most common genetic cause of intellectual disability after Down's syndrome Males are more severely affected by than females. CLINICAL FEATURES: Long face Hyperextensible joints High Arched Palate Mitral valve prolapse Large Mandible Large Ears Large testis/ macroorchidism ( In post- pubeal males) OTHER OPTIONS : Seckel syndrome- elongated bird facies, beak like nose, microcephaly Rett syndrome- acquired microcephaly Rubinstein Taybi syndrome- microcephaly, micrognathia, high arched palate, low set ears, angulated thumb.