Double Isochromosome X, a Rare Cytogenetic Variant of Turner Syndrome: A Case Report and a Review of the Literature.

Turner Syndrome (TS) is a genetic disorder caused by total or partial loss of an X chromosome. The isochromosome X (i(X)) is a known variant of TS, however, double i(X) is a very rare variant, reported very few times in the literature. We report on a rare case of TS with double i(X). This is an 11-year-old female patient , addressed to the medical genetics consultation for short stature and facial features suggestive of TS. We performed a constitutional postnatal karyotype from a peripheral blood sample, with lymphocyte culture, and an R band analysis, performed on 70 metaphases. Metaphases analysis in our patient identified the presence of three cell populations: 45,X[22]/46,X,i(X)(q10)[30]/47,X,i(X)(q10),i(X)(q10) [18]. The first has total chromosome X monosomy, the second with a normal X chromosome and one isochromosome of the long arm of the other X chromosome and the third with a normal X chromosome and two isochromosomes of the long arm of the X chromosome. A control cell culture was performed from a second blood sample of the patient and confirmed the abnormality. This paper will discuss this case in comparison with other rare cases described, as well as the formation of the double isochromosome, based on the literature.