Pregnancy and life after preimplantation genetic diagnosis of Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome - Fetal phenotypes with special reference to the syndrome-specific internal malformation pattern

Background

Autosomal‐recessive SLOS is caused by mutations in the DHCR7 gene. It is defined as a highly variable complex of microcephaly with intellectual disability, characteristic facies, hypospadias, and polysyndactyly. Syndrome diagnosis is often missed at prenatal ultrasound and fetal autopsy

Methods

We performed autopsies and DHCR7 gene analyses in eight fetuses suspected of having SLOS and measured cholesterol values in long‐term formalin‐fixed tissues of an additional museum exhibit

Results

Five of the nine fetuses presented classical features of SLOS, including four cases with atrial/atrioventricular septal defects and renal anomalies, and one with additional bilateral renal agenesis and a Dandy‐Walker cyst. These cases allowed for diagnosis at autopsy and subsequent SLOS diagnosis in two siblings. Two fetuses were mildly affected and two fetuses showed additional holoprosencephaly. These four cases and the exhibit had escaped diagnosis at autopsy. The case with bilateral renal agenesis presented a novel combination of a null allele and a putative C‐terminus missense mutation in the DHCR7 gene

Conclusions

In view of the discrepancy between the prevalence of SLOS among newborns and the carrier frequency of a heterozygous DHCR7 gene mutation, the syndrome‐specific internal malformation pattern may be helpful not to miss SLOS diagnosis in fetuses at prenatal ultrasound and fetal autopsy

Healthy Baby Born to a Robertsonian Translocation Carrier following Next-Generation Sequencing-Based Preimplantation Genetic Diagnosis: A Case Report

Preimplantation genetic diagnosis (PGD) is well established method for treatment of genetic problems associated with infertility. Moreover, PGD with next-generation sequencing (NGS) provide new possibilities for diagnosis and new parameters for evaluation in, for example, aneuploidy screening. The aim of the study was to report the successful pregnancy outcome following PGD with NGS as the method for 24 chromosome aneuploidy screening in the case of Robertsonian translocation. Day 3 embryos screening for chromosomal aneuploidy was performed in two consecutive in vitro fertilization (IVF) cycles, first with fluorescent in situ hybridization (FISH), and then with NGS-based protocol. In each IVF attempt, three embryos were biopsied. Short duration of procedures enabled fresh embryo transfer without the need for vitrification. First IVF cycle with the embryo selected using PGD analysis with the FISH method ended with pregnancy loss in week 8. The second attempt with NGS-based aneuploidy screening led to exclusion of the following two embryos: one embryo with 22 monosomy and one with multiple aneuploidies. The transfer of the only euploid blastocyst resulted in the successful pregnancy outcome. The identification of the euploid embryo based on the NGS application was the first successful clinical application of NGS-based PGD in the case of the Robertsonian translocation carrier couple.

Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive, multiple congenital malformation and intellectual disability syndrome, with clinical characteristics that encompass a wide spectrum and great variability. Elucidation of the biochemical and genetic basis for SLOS, specifically understanding SLOS as a cholesterol deficiency syndrome caused by mutation in DHCR7, opened up enormous possibilities for therapeutic intervention. When cholesterol was discovered to be the activator of sonic hedgehog, cholesterol deficiency with inactivation of this developmental patterning gene was thought to be the cause of SLOS malformations, yet this explanation is overly simplistic. Despite these important research breakthroughs, there is no proven treatment for SLOS. Better animal models are needed to allow potential treatment testing and the study of disease pathophysiology, which is incompletely understood. Creation of human cellular models, especially models of brain cells, would be useful, and in vivo human studies are also essential. Biomarker development will be crucial in facilitating clinical trials in this rare condition, because the clinical phenotype can change over many years. Additional research in these and other areas is critical if we are to make headway towards ameliorating the effects of this devastating condition.