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Fragile X syndrome (FXS) is a genetic neurodevelopmental disorder characterized by mild-to-moderate intellectual disability. [1] The average IQ in males with FXS is under 55, while about two thirds of affected females are intellectually disabled.
Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder most frequently seen in male premutation carriers of Fragile X syndrome (FXS) over the age of 50. [ 4 ] [ 5 ] The main clinical features of FXTAS include problems of movement with cerebellar gait ataxia and action tremor .
These mutations disrupt the 3-dimensional shape of FMRP or prevent the protein from being synthesized, leading to the signs and symptoms of fragile X syndrome. A CGG sequence in the FMR1 gene that is repeated between 55 and 200 times is described as a premutation. Although most individuals with the premutation are intellectually normal, some of ...
Fragile X-associated primary ovarian insufficiency (FXPOI) is the most common genetic cause of premature ovarian failure in women with a normal karyotype 46,XX. [1] The expansion of a CGG repeat in the 5' untranslated region of the FMR1 gene from the normal range of 5-45 repeats to the premutation range of 55-199 CGGs leads to risk of FXPOI for ovary-bearing individuals. [2]
The first trinucleotide repeat disease to be identified was fragile X syndrome, which has since been mapped to the long arm of the X chromosome. Patients carry from 230 to 4000 CGG repeats in the gene that causes fragile X syndrome, while unaffected individuals have up to 50 repeats and carriers of the disease have 60 to 230 repeats.
Sherman theorized that the gene responsible for fragile X syndrome becomes mutated through a two-step process. The first mutation, called the 'premutation', doesn't cause any clinical symptoms. A second mutation was required to convert the 'premutation' into a 'full mutation' capable of causing the clinical symptoms associated with fragile X ...
The condition is commonly inherited in connection with fragile X syndrome (FXS), which is also the second most common genetic cause of intellectual disability. [1] The condition is also a rare sign of McCune–Albright syndrome. [2] The opposite of macroorchidism is called microorchidism, which is the condition of abnormally small testes.
Child born prematurely (born before 37 weeks). The use of toxic substances in pregnancy, particularly alcohol, can lead to developmental delay if they affect the neurological development of the fetus, such as in fetal alcohol syndrome. Even though there are many known causes of delay, some children will never receive a diagnosis. [3]