Familial complex chromosome rearrangement (CCR) involving 5 breakpoints on chromosomes 1, 3 and 13 in a severe oligozoospermic patient

Excerpt

Complex chromosome rearrangement (CCR) is a structural chromosomal aberration that involves three or more breakpoints located on two or more chromosomes. CCRs may be grouped into three major categories depending on different characteristics. According to chromosome numbers involved and the breakpoints per chromosome, CCR can be classified into double two-way exchanges, three-way exchanges, and more complicated or the exceptional CCRs [17, 26]. Based on the origin or means of transmission, CCR can be divided into familial and de novo [11,18]. Depending on unchanging or loss/gain of genetic materials, CCR can be classified into balanced or unbalanced. It is well-known that carriers of unbalanced CCR may lead to significant clinical consequences such as dysmorphic features, multiple congenital anomalies and mental retardation or subnormality in their offspring [2, 3] while carriers of the balanced CCR usually have normal phenotypes and remain undetected in family members through multiple generations. Recently, studies have revealed that carriers of the balanced CCR are prone to infertility and recurrent abortions, and predispose to have offspring with unbalanced rearrangements due to either malsegregation of the derivative chromosomes or formation of a recombinant chromosome [17]. In general, most familial cases have a normal phenotype with apparently balanced rearrangements [20]. In contrast, half of de novo CCRs are unbalanced, and remaining half are apparently balanced but associated with multiple structural anomalies as well as mental retardation [7]. …