Preimplantation genetic diagnosis (PGD) for SHOX-related haploinsufficiency in conjunction with trisomy 21 detection by molecular analysis

Purpose Development of a molecular PGD protocol for a male with an X-linked deletion in the SHOX gene region, located in the pseudoautosomal region of the X/Y chromosomes. Due to excessive recombination in this region, the deletion can be found in male offspring. Methods We developed a 13 marker multiplex fluorescent PCR protocol: 3 markers within the deleted SHOX region, 5 flanking markers, 3 informative markers on chromosome 21 (advanced maternal age) and 2 markers for sex determination. Results Of four embryos, two wild type males, diploid for chromosome 21 were transferred resulting in twin boys. One embryo was an affected female and another embryo was Turner. Amniocentesis confirmed the implanted embryos were males (46XY), with no recombinations. Conclusions While many X-linked disorders can be analyzed by sexing, genes located in the pseudoautosomal regions have high XY recombination rates, requiring multiple markers to enable an accurate diagnosis.