<prompt> All are true about fragile X syndrome except:Large headLarge noseLarge earLarge testis  <response>: In fragile-X syndrome, there would be a small nose, not large. Fragile--X syndrome or Main-Bell Syndrome: Trinucleotide repeat mutation of CGG Characteristics Hyperextensible joint or high-arched palate Mitral valve prolapse FMR1 P deficiency fragile X mental retardation 1 protein- upregulates the metabotropic glutamate receptor mGluR 5 pathway and alters the expression of matrix metalloproteinase MMP 9 Repeating the sequence of 3 nucleotides CGG, recurrent otitis media AutismAttention deficit-hyperactivity disorderAnxiety Giant braim macrocephaly and giant testis macroorchidism Intellectual disability i.e., mental retardation Long face with a large mandible Eveed ear X-Linked disorder The most common genetic cause of mental retardation is Down;s syndrome Fragile X syndrome. Sherman;s Paradox: Risk of expressing mental retardation in fragile X syndrome increases in later generations anticipation Fragile X-associated tremor or ataxia: Intention tremors and cerebellar ataxia, which may progress to parkinsonism Ref: Nelson textbook of pediatrics 21st edition Pgno: 671 