Turner’s syndrome, also known as ‘monosomy X’, is a genetic disorder that occurs in 1/2,500 female births and is hypothesized to result from haploinsufficiency of certain genes expressed from both sex chromosomes that escape X inactivation. While the classic karyotype related to Turner’s syndrome is 45,X, the majority of those affected actually have a mosaic chromosomal complement, most often with a second normal cell line (46,XX). The resulting phenotype is variable and related to the underlying chromosomal pattern, but it is characterized by three cardinal features: short stature (around 100%), ovarian failure (>90%) and congenital lymphedema (>80%). In this paper we report a molecular and cytogenetic investigation of a 26-year-old female with non-mosaic 45,X karyotype, who has a stature of 170 cm without GH treatment, and whose only apparent Turner feature is gonadal dysgenesis. The only possible explanation for the absence of Turner phenotype is the hidden mosaicism combined with an untreated gonadal dysgenesis. Our results support the theory that significant ascertainment bias exists in our understanding of Turner’s syndrome.

Keywords:
45,X, Hidden mosaicism, Karyotype, Mosaicism, Tall stature, Turner’s syndrome
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© 2010 S. Karger AG, Basel
2010
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