Preimplantation genetic risk reduction: a new dilemma in the era of chromosomal microarrays and exome sequencing.

New technologies are revealing genetic variants of unknown significance (VUS), raising questions about the indications that call for preimplanation genetic diagnosis (PGD). Two couples requesting PGD for VUS are presented. The first couple requested PGD for Lynch syndrome. Whole exome sequencing identified in a healthy male with a family history of Lynch-associated tumours, a MLH1 missense variant. The variant had not been reported as pathogenic, but was predicted as damaging by algorithms. The second couple had a child diagnosed with pervasive developmental disorder and intellectual disability, carrying a microduplication on chr:Xp.22.3, and a microdeletion on chr:17q21.31. The maternally inherited X linked microduplication was also present in the mother's healthy brother and daughter, whereas the chr17 microdeletion was a de-novo event. As chromosomal microarrays and whole-exome sequencing are becoming standard tests, couples are requesting PGD for these VUS. The risk of possible genetic diseases can be reduced by carrying out PGD for uncertain findings, yet will inevitably lead to the birth of affected children despite the transfer of embryos that are not carriers of the familial variants. Findings of unknown significance demand urgent discussion and guidelines for their use as a risk-reduction measure in the preimplantation setting.

Preimplantation genetic diagnosis as a strategy to prevent having a child born with an heritable eye disease.

BACKGROUND: In developed countries, genetically inherited eye diseases are responsible for a high percentage of childhood visual impairment. We aim to report our experience using preimplantation genetic diagnostics (PGD) in order to avoid transmitting a genetic form of eye disease associated with childhood visual impairment and ocular cancer. MATERIAL AND METHODS: Retrospective case series of women who underwent in vitro fertilization (IVF) and PGD due to a familial history of inherited eye disease and/or ocular cancer, in order to avoid having a child affected with the known familial disease. Each family underwent genetic testing in order to identify the underlying disease-causing mutation. IVF and PGD treatment were performed; unaffected embryos were implanted in their respective mothers. RESULTS: Thirty-five unrelated mothers underwent PGD, and the following hereditary conditions were identified in their families: albinism (10 families); retinitis pigmentosa (7 families); retinoblastoma (4 families); blue cone monochromatism, achromatopsia, and aniridia (2 families each); and Hermansky-Pudlak syndrome, Leber congenital amaurosis, Norrie disease, papillorenal syndrome, primary congenital cataract, congenital glaucoma, Usher syndrome type 1F, and microphthalmia with coloboma (1 family each). Following a total of 88 PGD cycles, 18 healthy (i.e., unaffected) children were born. CONCLUSIONS: Our findings underscore the importance an ophthalmologist plays in informing patients regarding the options now available for using prenatal and preimplantation genetic diagnosis to avoid having a child with a potentially devastating genetic form of eye disease or ocular cancer. This strategy is highly relevant, particularly given the limited options currently available for treating these conditions.