Klinefelter Syndrome with Azoospermia：Identification of a Neocentromic Y Chromosome  with No Detectable DYZ3 Centromeric Sequence

Background Individuals with rare cytogenetic variants have contributed to our understanding of the genetics of sex chromosome and its disorders. Here, we report on a 23 years old man with a de novo 47,XX,+mar.ish der(Y)neo(Y)(pter-->p11.2::q11.23-->neo-->q11.23-->qter)(DYZ3-,SRY+,WCPY+) chromosome complement, accompanying with azoospermia and some of other clinical features suggestive of Klinefelter's Syndrome. The constitution of the patient was verified by GTG-banding, QFQ-banding, Fluorescence in Situ Hybridization and Polymerase Chain Reaction. Accordingly, we report the finding of a structurally abnormal chromosome Y with no detectable DYZ3 centromeric sequence and with no detection of AZF a, AZF b and AZF c, with clinical features suggestive of Klinefelter's Syndrome. This is the first reported case of Klinefelter's Syndrome involving a neocentromic Y among previously described cases with a neocentromere. Case presentation we report on a 23 years old man with a de novo 47,XX,+mar.ish der(Y)neo(Y)(pter-->p11.2::q11.23-->neo-->q11.23-->qter)(DYZ3-,SRY+,WCPY+) chromosome complement, accompanying with azoospermia and some of other clinical features suggestive of Klinefelter's Syndrome. The constitution of the patient was verified by GTG-banding, QFQ-banding, Fluorescence in Situ Hybridization FISH and Polymerase Chain Reaction PCR. Conclusions It can be inferred that a neocentromic Y is formed by identification of FISH, PCR and the fact that this markerof Y chromosome is present in 100% of peripheral blood cells and has been efficiently retained through cell divisions despite the absence of the endogenous cen­tromere region. To our knowledge, this is the first reported case of Klinefelter's Syndrome involving a neocentromic Y among previously described cases with a neocentromere, which adds to the catalog of chromosomal aberrations. The present study not only improves the understanding of karyotype/phenotype relationships between neocentric marker Y chromosomes and KFS male infertility, but also supports the hypothesis that the combined application of molecular cytogenetic analysis might help to identify breakpoints, origins, and the constitution of the marker chromosomes.