Background and objective

A small supernumerary marker chromosome (sSMC) is a rare structurally abnormal chromosome in which no part can be identified by conventional cytogenetic banding technique. There is little known about the association of marker chromosomes with male infertility. We performed a molecular cyto-genetic characterization sSMCs and investigated their association with male infertility.

Methods

Among 4230 infertile male patients who underwent cytogenetic analyses from January 2008 to December 2018, the records of 15 patients who were diagnosed with sSMCs were reviewed. After ini-tial infertility evaluation, the patients received additional genetic tests including G-bands by trypsin using Giemsa (GTG-banding), Nucleolar organizer region (NOR) banding, Fluorescence in situ hybridization (FISH), and array comparative genomic hybridization (aCGH) analyses to further char-acterize and identify the origin of their marker chromosome. Testis biopsy was performed for the azoospermic patients to evaluate spermatogenic status.

Results

Among 15 infertile males with sSMCs, eight had nonobstructive azoospermia, five had severe oligozo-ospermia, and two had sperm concentrations above the lower normal limit. The marker chromosomes were identified as Y ring chromosomes (n = 8), an isodicentric Y chromosome (n = 1), a neocen-tromere Y chromosome (n = 1), a derivative chromosome 1 (n = 1), and an acrocentric short arms (n = 4). 

Conclusion

Marker chromosomes appear to be a rare genetic cause of male infertility. Additional cytogenetic tests, including NOR banding, FISH, and aCGH, could help to characterize the origin of the marker chromosome. Appropriate genetic counseling for couples with infertility caused by a marker chromo-some should be recommended.