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The symptoms and prognosis of tetrasomy 9p are highly variable. [3] The severity of the symptoms is largely determined by the size of the isochromosome, the specific regions of chromosome 9p that are duplicated, as well as the number and type of tissues that are affected in the mosaic form.
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 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]
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 .
Klinefelter syndrome is not an inherited condition. The extra X chromosome comes from the mother in approximately 50% of the cases. Maternal age is the only known risk factor. Women at 40 years have a four-times-higher risk of a child with Klinefelter syndrome than women aged 24 years. [14] [34] [35]
Other conditions, such as Beckwith–Wiedemann syndrome, are associated with abnormalities of imprinted genes on the short arm of chromosome 11. Chromosome 14 is also known to cause particular symptoms such as skeletal abnormalities, intellectual disability, and joint contractures , among others.
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.
46,XX/46,XY chimeric or mosaic is associated with a wide spectrum of different physical presentations, with cases ranging from having a completely normal male or female phenotype [7] [8] [9] to some cases having ovotesticular syndrome. Due to this variation, genetic testing is the only way to reliably make a diagnosis. [11] [12] [13] [6]