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Updated: Jun 1, 2026

Exploring X Chromosomal Aberrations in Ovarian Cells by Using Fluorescence In Situ Hybridization
Published on: April 7, 2023
Tetrasomy and pentasomy of the X chromosome
Edith Schoubben1, Karin Decaestecker, Koen Quaegebeur
1Stedelijk Ziekenhuis, Brugsesteenweg 90, 8800 Roeselare, Belgium. eschoubben@yahoo.com
Unlabelled:
We describe a newborn girl with a life-threatening laryngomalacia and extreme hypotonia. Genetic analysis revealed the very rare genetic condition mosaicism of 48,XXXX and 49,XXXXX (50/50). We here state that the degree of early hypotonia constitutes an important early prognostic feature in this syndrome. The timely insertion of a gastrostomy is warranted in order to prevent aspiration.
Conclusion:
A karyotype is mandatory in female newborns with moderate to severe hypotonia in order to exclude polyploid mosaicism of the X chromosome. An 'overall prognosis' for 48,XXXX and 49,XXXXX girls is difficult to provide towards parents in line with a well-known, substantial variability in outcome for all polysomy X infants.
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