Crouzon syndrome: preimplantation genetic testing for a familial case with a whole and a mosaic variant of the disease.

Crouzon syndrome, which is a hereditary craniosynostosis, can be the result of inheritance from either parent, as well as de novo mutations in the FGFR2 gene. With a confirmed molecular genetic diagnosis, preimplantation genetic testing for monogenic diseases (PGT-M) is available for high-risk families. However, there is currently little information in the literature about using this approach to prevent this condition. The aim of our study was to describe the clinical case of IVF/ICSI with PGT-M for Crouzon syndrome with a successful outcome and confirmatory diagnostics. PGT-M was planned and performed for a married couple (aged 24 and 25), in which the husband had Crouzon syndrome. The husband's father had a milder form of Crouzon syndrome and the pathogenic variant of the FGFR2 gene was in a mosaic form. During preparation, a testing system was selected for the pathogenic variant NM_000141.5(FGFR2):c.1007A>G (p.Asp336Gly) of the FGFR2 gene, and gene-linked polymorphic microsatellite markers. The STR markers in the husband's father excluded chimerism for the pathogenic variant and indicated mosaicism with the involvement of germ cells. Molecular genetic analysis was performed using а nested PCR, with detection by fragment analysis for STRs and restriction analysis of the pathogenic variant. During the IVF program, superovulation stimulation and embryological procedures were performed according to standard protocols. Fertilization was achieved using the ICSI method, and blastocyst biopsy was done on the sixth day of development. For PGT-M, a direct analysis of pathogenic variants and an indirect analysis of selected informative STRs were used. The thawed embryos were transferred based on the results of preimplantation testing. We selected twelve STRs flanking the FGFR2 gene, eight informative ones were used during PGT-M. In the IVF program, 15 mature oocytes were obtained, then four blastocysts were biopsied. One of the four embryos inherited a normal paternal chromosome, the other three had the pathogenic variant and the associated risk haplotype. A singleton pregnancy has occurred as a result of embryo transfer recommended after PGT-M. Following the child's birth, molecular diagnostics were performed, confirming the PGT-M result. The presented clinical case provides an effective example of IVF with PGT-M to prevent the birth of affected children in families with hereditary craniosynostosis.