47,XY,+der(X)t(X;18)(p11.4;p11.22): A Unique Aneuploidy Associated with Klinefelter Syndrome due to an Extra Derivative X Chromosome Inherited Maternally.

A derivative X chromosome formed by translocation involving an X chromosome and a chromosome 18 in a Klinefelter syndrome (KS) patient with a 47,XXY karyotype has not been reported before. In this study, we present the clinical and molecular cytogenetic characteristics. The patient presented with small testes and azoospermia. G-banding analysis identified the karyotype as 47,XY,del(X)(p?11.4). Array CGH detected a 10.36-Mb duplication of chromosome region 18p11.22p11.32 (14,316-10,377,516) and a 111.18-Mb duplication of chromosome region Xp11.4q28 (61,931, 689-155,111,583), in addition to the normal chromosome 18 and an X chromosome. FISH results further revealed the extra 18p located at the end of the short arm of a deleted X chromosome, forming a derivative X chromosome. Finally, we identified the karyotype of the patient as 47,XY,+der(X)t(X;18)(p11.4;p11.22). The derivative X chromosome was maternally inherited. To our knowledge, this rare karyotype has not yet been reported in the literature. The present study may suggest a novel karyotype associated with KS.