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What is All are true about fragile X syndrome except: and explain in detail?
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 Autism/Attention deficit-hyperactivity disorder/Anxiety 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