Fragile X syndrome is a hereditary condition which results in a variety of developmental difficulties such as learning disabilities and cognitive impairment. Normally, men are more seriously affected by this disease than females.
Affected individuals normally have delayed development of language and speech by age two. Most men with fragile X syndrome have mild to moderate intellectual impairment, while roughly one-third of affected females have been intellectually disabled. Children with fragile X syndrome may also have stress and hyperactive behaviour like fidgeting or spontaneous actions. They might have attention deficit disorder (ADD), which comprises a diminished ability to keep focus and problem focusing on particular tasks. About one-third of people with fragile X syndrome have characteristics of autism spectrum disorders that influence communication and social interaction.
Most men and approximately half of females with fragile X syndrome have characteristic physical characteristics that become more evident with age. These attributes comprise a long and slim face, big ears, a prominent jaw and brow, unusually flexible palms, level feet, also in men, enlarged testicles (macroorchidism) following puberty.
Fragile X syndrome is generally because of an expansion of this CGG triplet repeat inside the Fragile X mental retardation 1 (FMR1) gene on the X chromosome. This results in insufficient fragile X mental retardation protein(FMRP), which is needed for normal maturation of the link between nerves. Identification is by genetic testing to ascertain the amount of CGG repeats at the FMRI gene. Regular is between 5 and 40 repeats, fragile X syndrome happens with over 200, and also a premutation is believed to be current when a centre number of repetitions happen. Testing for premutation carriers can enable for genetic counselling.
Signs and symptoms of fragile X syndrome
Most young children don’t show any physical signs of FXS. It isn’t until puberty that bodily characteristics of FXS start to develop. Besides intellectual impairment, notable features of this syndrome may include an elongated face, big or protruding ears, horizontal feet, bigger testes (macroorchidism), also reduced muscle tone. The speech might be littered or nervous. Behavioral characteristics could incorporate stereotypic movements (e.g., hand-flapping) and irregular social growth, especially shyness, restricted eye contact, memory issues, and a problem with face communicating. Some people with fragile X syndrome also fulfill the diagnostic criteria for autism.
Males with a complete mutation display almost entire penetrance and will therefore almost always exhibit symptoms of FXS, whereas females with a complete mutation normally display a penetrance of approximately 50 percent as a consequence of using an instant, regular X chromosome. Females with FXS might have symptoms which range from mild to severe, though they’re usually less affected than men.
Fragile X syndrome causes
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 chromosome, most commonly an increase in the number of CGG trinucleotide repeats in the 5′ untranslated region of FMR1. Mutation at that site is located in 1 out of approximately every 2000 men and 1 from approximately every 259 females. Incidence of the disease itself is roughly 1 in every 3600 men and 1 in 4000–6000 females. Though this accounts for more than 98 percent of instances, FXS may also happen as a consequence of point mutations affecting FMR1.
Between 45-54 repeats is regarded as a “gray zone”, using a premutation allele normally regarded to be between 55 and 200 repeats in length. People with fragile X syndrome have a complete mutation of their FMR1allele, together with over 200 CGG repeats. In such people with a repeat growth over 200, there’s methylation of the CGG repeat expansion and FMR1promoter, resulting in the silencing of this FMR1 receptor along with a scarcity of its own product.
This methylation of FMR1 at chromosome group Xq27.3 is thought to lead to constriction of the X chromosome which looks ‘brittle’ under the microscope in the point, a phenomenon which gave the syndrome its name. 1 study discovered that FMR1 silencing is evidenced by the FMR1 mRNA. The FMR1 mRNA includes the transcribed CGG-repeat tract as a portion of their 5′ untranslated region, which hybridizes to the complementary CGG-repeat section of the FMR1 gene to make an RNA·DNA duplex.
