Fragile X syndrome, also termed Martin-Bell syndrome or marker X syndrome, is the most common cause of inherited mental retardation. Fragile X syndrome has been found in all major ethnic groups and races, and is caused by an abnormality (mutation) in the FMR1 gene. FMR1 is a gene located . Fragile X syndrome is caused by the expansion or lengthening of the FMR1 gene on the X chromosome, known as a gene mutation. The X chromosome is one.

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Males are usually more severely affected than females. Investigational Therapies The development of animal models for fragile X syndrome studies over the last two decades resulted in great anticipation that effective drug treatments could be discovered. The first complete DNA sequence of the repeat expansion in someone with the full mutation was generated by scientists in using SMRT sequencing.

Methylation is a chemical change to the DNA that carries the genetic code of a gene and the abnormal methylation associated with fragile X syndrome causes the gene to be unable to produce FMRP, the protein made by the FMR1 gene, needed for normal development.

Some symptoms of the following disorders can be similar to those of fragile X syndrome.

Fragile X Syndrome

Terracciano A, Chiurazzi P. These symptoms can include a large head, long face, prominent forehead and chin, protruding ears, loose joints and large testes. However, about four times as many females appear to be carriers of the altered gene as do males 1: The fragile X premutation: Prenatal testing with chorionic villus sampling or amniocentesis allows diagnosis of FMR1 mutation while the fetus is in utero and appears to be reliable.

Genetic X-linked dominant [1]. The main difficulties in individuals with FXS are with working and short-term memory, executive functionvisual memory, visual-spatial relationships, and mathematics, with verbal abilities being relatively spared. Because the premutation is relatively stable when transmitted from father to daughter, the daughters almost never are affected with fragile X syndrome.

Diagnosis is very difficult especially if there is only one male with intellectual disability in a family. What is Fragile X syndrome? Getting treatment early can help. Some girls have no signs at all.


Autism Research Centre UK. Centers for Disease Control and Prevention. Evidence from mouse models shows that mGluR5 antagonists blockers can rescue dendritic spine abnormalities and seizures, as well as cognitive and behavioral problems, and may show promise frajip the treatment of FXS. The subsequent abnormalities in the formation and function of synapses and development of neural circuits result in impaired neuroplasticityan integral part of memory and learning.

Journal of Abnormal Child Psychology. Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual.

What causes Fragile X Syndrome | Fragile X Association of Australia

European Journal of Human Genetics. Occasionally, in some individuals with repeats there will be some minor instability such that these individuals will have several more or less repeats than their parents.

Individuals with FXS may present anywhere on a continuum from learning disabilities in the context of a normal intelligence quotient IQ to severe intellectual disabilitywith an average IQ of 40 in males who have complete silencing of the FMR1 gene.

Fragile X syndrome FXS is a genetic disorder.

Normally, the gene makes a protein you need for brain development. Refractive errors in patients with FXS are also common. The syndrome became known as the fragile X syndrome because some individuals with the disorder were found to have a segment of their X chromosome that appeared to be broken or fragile although not completely disconnected. However, in a premutation individual, CGG length is only significantly correlated with the central executive, not with either phonological memory or visual—spatial memory.

Males have one X and one Y chromosome and females have two X chromosomes. Alexithymia Attention deficit hyperactivity disorder Anxiety disorder obsessive—compulsive disorder Late talker Epilepsy Fragile X syndrome Hyperlexia Savant syndrome Sensory processing disorder Intellectual disability Developmental coordination disorder Multiple complex developmental disorder.

Pairs of human chromosomes are numbered from 1 through 22 and the sex chromosomes are designated X and Y. Retrieved 10 May Fragile X syndrome co-occurs with autism in many cases and is a suspected genetic cause of the autism in these cases.


What is Fragile X syndrome?

Incidence of the disorder itself is about 1 in every males and 1 in — females. 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 chromosomemost commonly an increase in the number of CGG trinucleotide repeats in the 5′ untranslated region of FMR1.

There are no cure for the underlying defects of FXS. Models and mechanisms of repeat expansion disorders: This technique is no longer used in the diagnosis of this syndrome because it is both less accurate and costlier than are molecular techniques.

Diagnosis, Treatment, and Research, 3 ed. Autism spectrum High-functioning autism Classic Autism Asperger syndrome Pervasive developmental disorder not otherwise specified Childhood disintegrative disorder Rett syndrome.

The CGG length is significantly correlated with central executive and the visual—spatial memory. In speech, the trend is not only in repeating the same phrase but also talking about the same subject continually. Alzheimer’s disease Huntington’s disease Creutzfeldt—Jakob disease chaperonins: Social withdrawal behaviors, including avoidance and indifference, appear to be the best predictors of ASD in FXS, with avoidance appearing to be correlated more with social anxiety while indifference was more strongly correlated to severe ASD.

D ICD – Renpenning syndrome is one of the chromosome X-linked intellectual disability disorders that affects males almost to the exclusion of females. This means that children born with Fragile X frequently appear in families with no previous history of intellectual disability. New medications are likely to become available to treat affected individual and the specialty clinics can assist parents with current information.

Behavioral characteristics may include stereotypic movements e. The absence or severe drajil of this protein leads to the symptoms of fragile X syndrome. However many women with the Fragile X premutation are able to conceive and family planning options are recommended.