X-linked dominant genetic disorder Fragile X syndrome Other names Martin–Bell syndrome,  Escalante syndrome Boy with protruding ears characteristic of fragile X syndrome Specialty Medical genetics , pediatrics , psychiatry Symptoms Intellectual disability , long and narrow face, large ears, flexible fingers, large testicles  Complications Autism features, seizures  Usual onset Noticeable by age 2  Duration Lifelong  Causes Genetic ( X-linked dominant )  Diagnostic method Genetic testing  Treatment Supportive care , early interventions  Frequency 1 in 4,000 (males), 1 in 8,000 (females)  Fragile X syndrome ( FXS ) is a genetic disorder characterized by mild-to-moderate intellectual disability .  The average IQ in males is under 55, while about two thirds of affected females are intellectually disabled.   Physical features may include a long and narrow face, large ears, flexible fingers, and large testicles .  About a third of those affected have features of autism such as problems with social interactions and delayed speech.  Hyperactivity is common, and seizures occur in about 10%.  Males are usually more affected than females.  This disorder and finding of Fragile X syndrome has an X-linked dominant inheritance.  It is typically caused by an expansion of the CGG triplet repeat within the FMR1 (fragile X mental retardation 1) gene on the X chromosome .  This results in silencing ( methylation ) of this part of the gene and a deficiency of the resultant protein (FMRP), which is required for the normal development of connections between neurons .  Diagnosis requires genetic testing to determine the number of CGG repeats in the FMR1 gene.  Normally, there are between 5 and 40 repeats; fragile X syndrome occurs with more than 200.  A premutation is said to be present when the gene has between 40 and 200 repeats; women with a premutation have an increased risk of having an affected child.  Testing for premutation carriers may allow for genetic counseling .  There is no cure.  Early intervention is recommended, as it provides the most opportunity for developing a full range of skills.  These interventions may include special education , speech therapy , physical therapy , or behavioral therapy .   Medications may be used to treat associated seizures , mood problems, aggressive behavior, or ADHD .  Fragile X syndrome is estimated to occur in 1.4 per 10,000 males and 0.9 per 10,000 females.  Contents 1 Signs and symptoms 1.1 Physical phenotype 1.2 Intellectual development 1.3 Autism 1.4 Social interaction 1.5 Mental health 1.6 Vision 1.7 Neurology 1.8 Working memory 1.9 Fertility 2 Causes 2.1 Inheritance 3 Pathophysiology 4 Diagnosis 5 Management 5.1 Medication 6 Prognosis 7 Research 8 History 9 References 10 External links Signs and symptoms [ edit ] Prominent characteristics of the syndrome include an elongated face and large or protruding ears. Most young children do not show any physical signs of FXS.  It is not until puberty that physical features of FXS begin to develop.  Aside from intellectual disability, prominent characteristics of the syndrome may include an elongated face, large or protruding ears , flat feet, larger testes ( macroorchidism ), and low muscle tone .   Recurrent otitis media (middle ear infection) and sinusitis is common during early childhood. Speech may be cluttered or nervous. Behavioral characteristics may include stereotypic movements (e.g., hand-flapping) and atypical social development, particularly shyness, limited eye contact, memory problems, and difficulty with face encoding. Some individuals with fragile X syndrome also meet the diagnostic criteria for autism . Males with a full mutation display virtually complete penetrance and will therefore almost always display symptoms of FXS, while females with a full mutation generally display a penetrance of about 50% as a result of having a second, normal X chromosome.  Females with FXS may have symptoms ranging from mild to severe, although they are generally less affected than males.