Mosaicism for an unbalanced Y;21 translocation in an infertile man: a case report

Abstract

Approximately 30 % of male infertility cases are considered ‘idiopathic’ and an additional 40 % have only insufficient/uncertain causes (e.g. varicocele, infections) [1]. It is also estimated that about 30 % of azoo-/oligozoospermia are caused by chromosomal abnormalities (such as 47,XXY or balanced translocations), Y-chromosomal deletions or mutations in genes involved in germ cell production and function [2]. Compared to newborns, infertile males have a higher prevalence of autosomal reciprocal translocations [3], but translocations involving the sex chromosomes are rare [4]. The frequency of Y;autosome translocations in the general population was estimated to be 1 in 2000 [5]. In the more common forms, the heterochromatic region of the long arm of the Y chromosome is translocated onto the short arm of acrocentric chromosomes and fertility is usually not affected in carriers [6]. In contrast, the rare translocations of the euchromatic part of the Y chromosome are frequently associated with azoospermia [7]. Whenever one of the Azoospermia Factor (AZF) regions on Yq is affected by the translocation, this can be considered the cause for azoo- or severe oligozoospermia [8]. Incorrect or incomplete X/Y pairing during meiosis leading to defective sex vesical formation and consequently to spermatogenetic arrest may be another explanation for infertility of Y;autosome translocation carriers [9, 10]. Translocation carriers have an increased risk for offspring with unbalanced chromosomal aberrations and patients with unbalanced Y;autosome translocations are frequently mentally retarded, depending on the affected autosomal region [11]. The frequency of unbalanced spermatozoa may vary considerably depending on the translocation and utilising fluorescence in situ hybridisation (FISH) may help in assessing the individual risk.