Preimplation Diagnosis for Single-Gene Disorders

Abstract

Single-gene disorders are the first group of indications for which preimplantation genetic diagnosis (PGD) was originally introduced 21 years ago, with the purpose of performing genetic testing before pregnancy, in order to establish only unaffected pregnancies and avoid the need for pregnancy termination, which is the major limitation of traditional prenatal diagnosis [1, 2]. Despite the requirement for ovarian hyperstimulation and in vitro fertilization (IVF), needed to perform genetic testing of oocyte or embryo prior to transfer, PGD has been accepted in most parts of the world [3, 4]. At least 10,000 PGD cycles were performed for single-gene disorders and, as will be shown below, is presently offered for some indications that have never been practiced in prenatal diagnosis, such as late-onset diseases with genetic predisposition, and preimplantation HLA typing, making PGD not only an alternative but also a complement to prenatal diagnosis [5–8]. The progress of PGD has been extensively reviewed, so the present book will mainly concentrate on those aspects of PGD that are useful for reproductive medicine and genetics practices, including available PGD approaches for different groups of genetic disorders, their accuracy, and major indications compared to prenatal diagnosis, and present practical details useful for the realization of PGD for each of the conditions described.