Fragile X syndrome is also called as Martin–Bell syndrome, or Escalante's syndrome is a genetic syndrome. Nearly half of all children with fragile X syndrome meet the criteria for a diagnosis of autism. It is an inherited cause of intellectual disability especially among boys. It is caused by defect in chromosome Xq 27.3 .
Aside from intellectual disability, prominent characteristics of the syndrome may include an elongated face, large or protruding ears, flat feet, larger testes and low muscle tone. Recurrent otitis media and sinusitis is common during early childhood. Speech may be cluttered or nervous.
Fragile X syndrome is a genetic disorder which occurs as a result of a mutation of the fragile X mental retardation 1 (FMR1)gene on the X chromosome, most commonly an increase in the number of CGG tri nucleotide repeats in the 5' un translated region of FMR1.
A Belgium screening study in 2003 estimated an overall prevalence of FXS in the general population of 2.3/10,000 (or 1 in 4,425). Other estimates suggest it is present in 1 in 4,000 males and 1 in 8,000 females but that this may be an underestimation. Prevalence depends on the population studied.The premutation is far more common.