What Is Fragile X Syndrome?

Fragile X syndrome is an inherited genetic disease that causes intellectual and developmental disabilities. Inherited means that the disease is passed down from parents to children through their genes. Fragile X syndrome is the most common hereditary source of mental disability in boys.

People with fragile X syndrome usually experience a range of developmental and learning problems. According to the Genetics Home Reference (GHR), fragile X syndrome is found in about one in every 4000 males and about one in every 8000 females. Males usually have more severe symptoms than females.

What Causes Fragile X Syndrome?

Fragile X syndrome is caused by a defect in the FMR1 gene located on the X chromosome. The X chromosome is one of two types of sex chromosomes(The other is the Y chromosome). Women have two X chromosomes while men have one X chromosome and one Y chromosome. The defect (mutation) on the FMR1 gene prevents the gene from properly making a protein called the fragile X mental retardation 1 protein.

This protein plays a role in the functioning of the nervous system. The exact function of the protein is not fully understood. A lack or shortage of this protein causes the symptoms characteristic of fragile X syndrome.

A genetic blood test can diagnose Fragile X. There is no cure. You can treat some symptoms with educational, behavioral, or physical therapy, and with medicines.

Indications for referring for fragile X:

Mental retardation, Development delay, Learning/behavioural difficulties, Speech delay, Autistic features, Asperger syndrome, Attention deficit disorder/attention deficit, hyperactivity, disorder (ADD/ADHD), Social dysfunction, Poor eye contact, Challenging behaviour, Large head, Hand flapping/biting, Dysmorphic facies

●َ A family history of fragile X syndrome, or male or female relatives with undiagnosed mental retardation.

● Individuals seeking reproductive counseling who have (a) a family history of fragile X syndrome or (b) a family history of undiagnosed mental retardation.

● Fetuses of known carrier mothers.

● Affected individuals or their relatives in the context of a positive cytogenetic fragile X test result who are seeking further counseling related to the risk of carrier status among themselves or their relatives. The cytogenetic test was used prior to the identification of the FMR1 gene and is significantly less accurate than the current DNA test. DNA testing on such individuals is warranted to accurately identify premutation carriers and to distinguish premutation from full mutation carrier women.

● Womens who are experiencing reproductive or fertility problems associated with elevated follicle stimulating hormone (FSH) levels, especially if they have (a) a family history of premature ovarian failure, (b) a family history of fragile X syndrome, or (c) male or female relatives with undiagnosed mental retardation.

 ● Men and women who are experiencing late onset intention tremor and cerebellar ataxia of unknown origin, especially if they have (a) a family history of movement disorders, (b) a family history of fragile X syndrome, or (c) male or female relatives with undiagnosed mental retardation.