Chromosomes Chromosomes Genes are segments of deoxyribonucleic acid (DNA) that contain the code for a specific protein that functions in one or more types of cells in the body. Chromosomes are structures within cells... read more 
are structures within cells that contain DNA DNA Genes are segments of deoxyribonucleic acid (DNA) that contain the code for a specific protein that functions in one or more types of cells in the body. Chromosomes are structures within cells... read more and many genes. A gene is a segment of deoxyribonucleic acid (DNA) and contains the code for a specific protein that functions in one or more types of cells in the body ( see Genes and Chromosomes Genes and Chromosomes Genes are segments of deoxyribonucleic acid (DNA) that contain the code for a specific protein that functions in one or more types of cells in the body. Chromosomes are structures within cells... read more for a discussion about genetics). Genes contain instructions that determine how the body looks and functions.
Fragile X syndrome is the most commonly diagnosed inherited cause of intellectual disability Intellectual Disability Intellectual disability is significantly below average intellectual functioning present from birth or early infancy, causing limitations in the ability to conduct normal activities of daily... read more , and boys are affected more often than girls. Fragile X syndrome is second only to Down syndrome Down Syndrome (Trisomy 21) Down syndrome is a chromosome disorder caused by an extra chromosome 21 that results in intellectual disability and physical abnormalities. Down syndrome is caused by an extra chromosome 21... read more 
as a cause of intellectual disability in boys. However, unlike Fragile X syndrome, Down syndrome is not inherited in most cases. For more information, see the National Fragile X Foundation.
The symptoms of Fragile X syndrome are caused by an abnormality of a specific gene on the X chromosome ( see Gene abnormalities Gene abnormalities Chromosomes are structures within cells that contain a person's genes. A gene is a segment of deoxyribonucleic acid ( DNA) and contains the code for a specific protein that functions in one... read more ). People have an excessive number of copies (more than 200) of a small segment of deoxyribonucleic acid (DNA). People with 55 to 200 extra copies are considered to have a premutation because, although they do not have the disorder, their offspring are at greater risk of having it.
Symptoms of Fragile X Syndrome
Children and adults with the syndrome may have physical, intellectual, and behavior problems. Features, which are often subtle, include delayed development; large, protruding ears; a prominent chin and forehead; and, in boys, large testes (most apparent after puberty). The joints may be abnormally flexible, and heart disease (mitral valve prolapse Mitral Valve Prolapse (MVP) Mitral valve prolapse is a disorder in which the valve flaps (cusps) bulge into the left atrium when the left ventricle contracts, sometimes allowing leakage (regurgitation) of blood into the... read more 
) may occur.
Children may have mild to moderate intellectual disability. Features of autism Autism Spectrum Disorders Autism spectrum disorders are conditions in which people have difficulty developing normal social relationships, use language abnormally or not at all, and show restricted or repetitive behaviors... read more may develop, including repetitive speech and behavior, poor eye contact, and social anxiety.
Women who have the premutation may go through menopause Menopause Menopause is the permanent end of menstrual periods and thus of fertility. For up to several years before and just after menopause, estrogen levels fluctuate widely, periods become irregular... read more 
at a much younger age, especially in their mid-30s.
People who have the premutation are at risk of Fragile X–associated tremor/ataxia syndrome Fragile X–Associated Tremor/Ataxia Syndrome Fragile X–associated tremor/ataxia syndrome is a genetic disorder that affects mostly men and causes tremor, loss of coordination, and deterioration of mental function. Fragile X–associated... read more (FXTAS), which causes tremor, loss of coordination, and deterioration of mental function.
Diagnosis of Fragile X Syndrome
DNA tests
Fragile X syndrome can be detected by DNA tests done after birth. (See also Next-generation sequencing technologies Next-generation sequencing technologies Genetic diagnostic technologies are scientific methods that are used to understand and evaluate an organism's genes. (See also Genes and Chromosomes.) Genes are segments of deoxyribonucleic... read more .)
The diagnosis of Fragile X syndrome is typically made when the child is school age or an adolescent. It is recommended that boys with autism and intellectual disability be tested for Fragile X syndrome, especially if their mother has relatives who have similar problems.
Treatment of Fragile X Syndrome
Speech, language, and occupational therapies
Sometimes drugs
Early intervention, including speech and language therapy and occupational therapy, can help children with Fragile X syndrome maximize their abilities.
Stimulants, antidepressants, and antianxiety drugs may be beneficial for some children.
More Information
The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
National Fragile X Foundation: Provides advocacy, education, support, and public and professional awareness programs and services
