[Genetic analysis of a case with mosaicism complex structural aberration of chromosome 18]

To determine the karyotype of a patient with mosaicism complex structural aberration of chromosome 18.

A male patient with a 2-year history of infertility presented at the Center of Reproductive Medicine of the Third Hospital of Peking University in October 2019 was selected as the study subject. Clinical data of the patient was collected. Peripheral blood sample was taken for chromosomal karyotyping, copy number variation (CNV) analysis and fluorescence in situ hybridization (FISH) assay. Semen sample was taken for single sperm CNV analysis.

The patient was found to have a karyotype of mos 47,XY,del(18)(q21q23),+r(18)(q21q23)[84]/46,XY,del(18)(q21q23)[9]/48,XY,del(18)(q21q23),+r(18)(q21q23)×2[6]/47,XY,del(18)(q21q23),+r(18)(q21q23×2)[1].ish 47,XY,del(18)(q21q23),+r(18)(q21q23)[84]/46,XY,del(18)(q21q23)[9]/48,XY,del(18)(q21q23),+r(18)(q21q23)×2[6]/47,XY,del(18)(q21q23),+r(18)(q21q23×2)[1]del(18)(q21q23)(D18Z1+,18p+,18q+,WCP18+),r(18)(q21q23)(WCP18+),r(18)(q21q23×2)(WCP18+). No pathogenic CNV was identified. Sequencing of 20 single sperms showed that 1 sperm was normal, 1 had yielded no result, 9 had harbored del(18q), 7 had harbored dup(18q)×2, and 2 had harbored dup(18q)×3. The dup/del fragments had both spanned approximately 33 Mb.

It is rare for carriers of complex structural and numerical abnormalities of chromosome 18 to have a normal phenotype. Based on the accurate cytogenetic and molecular analyses and the single sperm CNV analysis, the influence of the aberrant karyotype on the gametogenesis may be evaluated.