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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.
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.
Females with one affected X chromosome and one normal X chromosome tend to have milder symptoms. Unlike many other types of intellectual disability, the genetics of these conditions are relatively well understood. [2] [3] It has been estimated there are ~200 genes involved in this syndrome; of these ~100 have been identified. [4]
FMR1 (Fragile X Messenger Ribonucleoprotein 1) is a human gene [5] that codes for a protein called fragile X messenger ribonucleoprotein, or FMRP. [6] This protein, most commonly found in the brain, is essential for normal cognitive development and female reproductive function.
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 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.
Fountain syndrome; Foville's syndrome; Fragile X syndrome; Fragile X-associated tremor/ataxia syndrome; Franceschetti–Klein syndrome; Frank–ter Haar syndrome; Fraser syndrome; Frasier syndrome; Freeman–Sheldon syndrome; Frey's syndrome; Froin's syndrome; Fryns syndrome; Functional somatic syndrome