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Journal of Applied Genetics 49(3), 2008, pp. 301-303

Turner syndrome mosaicism: an unusual case with a de novo large dicentric marker chromosome: mos 45,X/46,X, ter rea(X;X)(p22.3;p22.3)

Anna Lisa Nucaro, Paola Melis, Maria Rosaria Casini, Rossano Rossino, Milena Cau, Maria Antonietta Melis, Sandro Loche

Abstract: X/X translocations are quite rare in humans. The effect of this anomaly on the phenotype is variable and depends on the amount of deleted material and whether the chromosomes are joined by their long or short arms. We report an unusual case of Turner syndrome mosaicism in a 16-year-old girl, who was referred to our Institute for primary amenorrhoea associated with short stature. Endocrine evaluation revealed hypergonadotropic hypogonadism, which required a study of the karyotype. Cytogenetic analysis, performed on peripheral blood leucocytes, showed a mos 45,X/46,X,ter rea (X;X)(p22.3;p22.3) de novo karyotype. The prevalent cell line was 45,X (90% cells). A second cell line (10% cells) showed a very large marker chromosome, similar to a large metacentric chromosome. FISH (fluorescent in situ hybridisation) and molecular analysis revealed that the marker chromosome was dicentric and totally derived from the paternal X chromosome.

Key words: FISH, marker der(X), mosaicism, Turner syndrome, X/X translocation

Correspondence: A.L. Nucaro, INN-CNR, Cittadella Universitaria, SS 554, bivio Sestu, 09042 Monserrato, Cagliari, Italy; e-mail:

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