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.