Diagnosing fragile X syndrome

An analysis of the diagnosis of fragile X syndrome can be offered to patients who have had amniocentesis or chorionic biopsy.

Fragile X syndrome or FXS is the most common monogenic genetic disease causing intellectual disability. The incidence of FXS is 1:7,000 in boys and 1:11,000 in girls.

FXS is caused by a defective FMR1 gene on the X chromosome, which is responsible for nerve cell development. Girls have two X chromosomes and if one of them is defective, they will get a milder form of the disease than boys who don't have another healthy X chromosome.

This disease is characterised by typical appearance and intellectual disability. Boys have more pronounced symptoms than girls.

80% of boys with this disease have intellectual disability. Boys with FXS have a large head, a prominent forehead and jaw, large protruding ears, enlarged testicles after puberty, a high-arched palate. Affected boys are more likely to have mitral valve prolapse and enlarged descending aorta. Behavioral disorders are a big problem with boys with FXS: they often experience hyperactivity, restlessness, problems with concentrating, shyness, poor eye contact, autistic behavior, angry outbursts and seizures.

35% of girls with this disease have intellectual disability. Girls with FXS have large protruding ears, a long and narrow face, hyperflexible finger joints, flat feet and high birth weight. As for behavioral disorders, they have problems with paying attention, shyness, poor eye contact, restlessness, low self esteem, depression, hyperactivity, nervous movements, inadequate laughing and clapping.

As of today, there is no cure for FXS, but it is possible to alleviate symptoms. FXS children need a special programme for studying in school as the regular programme is too difficult for them. Heart defects may need surgical correction. Seizures may need anticonvulsant therapy. Antidepressant medications are used for alleviating agressiveness, mood swings and hyperactivity.

Fragile X syndrome analysis response comes 21 days after the invasive procedure.

The cost of the study includes contamination of the chorion and/or amnion cells with maternal material. The cost of a chorionic biopsy or amniocentesis is added to the price.