Fragile X syndrome

Population studies suggest a prevalence of FXS in 1 in 4,000 males and 1 in 8,000 females1

Fragile X syndrome is a genetic disorder that affects intellectual and developmental functioning. It is the most common inherited cause of intellectual disability and autism spectrum disorder. Fragile X syndrome is caused by a repeat expansion in the FMR1 gene, which is responsible for producing a protein necessary for normal brain development. The mutation in the FMR1 gene causes a disruption in the production of the fragile X mental retardation protein (FMRP). Without adequate FMRP, the brain does not function properly, leading to the characteristic features of fragile X syndrome.

Clinical utility

When is it recommended?

  • You want to find out the cause of fertility problems
  • You want to know the risk of having affected offspring
  • In the context of fertility, the study of Fragile X syndrome is recommended for women with fertility problems related to elevated FSH concentrations
  • Young women with low ovarian reserve or early menopause.

Test specification  

Technique Variant types TAT Sample requirements
TP - PCR STR 3 weeks EDTA Blood, Amniotic Fluid,
CVS (In case of Prenatal) and
3-4 ml Maternal Blood in EDTA for MCC


  1. Crawford, D. C., Acuna, J. M., & Sherman, S. L. (2001). FMR1 and the fragile X syndrome: human genome epidemiology review. Genetics in Medicine, 3(5), 359–371.


How is fragile X syndrome inherited?

Fragile X syndrome is inherited in an X-linked dominant manner. This means that both males and females can be affected, but males are typically more severely affected. Females can be carriers of the condition.

What are the symptoms of fragile X syndrome?

How is fragile X syndrome diagnosed?

How does fragile X syndrome testing impact in vitro fertilization (IVF)?

Can fragile X syndrome testing be done during pregnancy?