Case report: elevated sperm aneuploidy levels in an infertile Robertsonian translocation t(21;21) carrier with possible interchromosomal effect

Somatic chromosomal abnormalities are frequently found in infertile men, particularly in those with low sperm count [1–5]. Studies in infertile men have demonstrated that 2–14% carry constitutional chromosomal abnormalities [1] Research in this area has become more relevant in the past few years with the advent of assisted reproductive therapies (ART), especially intracytoplasmatic sperm injection (ICSI). ICSI has been extremely successful for the treatment of male infertility, but transmission of cytogenetic defects to offspring is a major concern and demonstrated to be reality [1], therefore it is recommended to investigate this. The incidence of chromosomal aberrations in infertile men depends on the definition of “infertility”, and is estimated to be approximately 5% in oligozoospermic men and 14% in azoospermic men [6]. Abnormalities mostly consist of numerical sex chromosome abnormalities (e.g. 47,XXY), balanced reciprocal translocations (reciprocal exchange between two chromosomes), inversions, Y-chromosome micro-deletions and balanced Robertsonian translocations (fusion of two acrocentric chromosomes, e.g. 13, 14, 15, 21, 22). Carriers of a balanced Robertsonian translocation show impaired gametogenesis to a variable degree and elevated levels of nullisomic or disomic sperm (3–40%, mean 15%) [1–5]. The fertilization with an aneuploid sperm results in monosomy or trisomy in the fetus [7, 8]. Furthermore fetal aneuploidies are a major cause of pregnancy loss and fetal malformations [9]. Here we report on a sperm aneuploidy screening of all chromosomes (1–22,X,Y) in an infertile patient showing low-frequency mosaicism of a balanced Robertsonian translocation involving both chromosomes 21.