RESUMO
Structural abnormalities of the Y chromosome affect normal testicular differentiation and spermatogenesis. The present case showed a rare monocentric derivative Y chromosome with partial duplication of Yp including the SRY gene and deletion of Yq12 heterochromatin. The karyotype was 46,X,der(Y) (pter-->q11.23::p11.2-->pter).ish der(Y)(DYZ3+,DYZ1-,SRY++), confirmed through a FISH study. Even though the patient possessed an abnormal Y chromosome, testicular biopsy showed normal testicular volumes in the proband, with gonadal hormonal levels in the normal range but bilateral varicocele and hypospermatogenesis. We speculate that the abnormal Y chromosome arose from sister chromatids during Y chromosome recombination or intra chromosomal NAHR (non-allelic homologous recombination) during meiosis in the patient's father or in the very early stages of embryogenesis. The derivative Y chromosome might interfere in the meiotic stage of spermatogenesis, leading to the developmental arrest of germ cells. The present case illustrates that the infertility phenotype can have various causes. Also, it emphasizes the importance of accurate and various genetic analyses and could aid in male infertility treatment.