Prenatal Evaluation of a Fetal Cystic Hygroma: An Unexpected Finding of a De Novo Fetal BRCA1 Deletion Case Report

Abstract

This case presents a novel occurrence of a de novo BRCA1 gene deletion in a fetus with a cystic hygroma. Chorionic villus sampling (CVS) was performed for chromosome G-banding analysis, demonstrating a normal karyotype: 46, XX. Chromosome microarray analysis performed as a reflex test revealed an 80 kb deletion on 17q21.31, encompassing the BRCA1 gene. Follow-up FISH analysis performed on parental blood samples yielded negative results, confirming that the deletion was de novo in the fetus. Subsequent anatomic ultrasound evaluation showed no identifiable structural defects, and it was concluded that the microdeletion was unlikely to be the cause of the cystic hygroma. Regardless, it will be imperative that the patient’s daughter be appropriately counseled regarding the implications of carrying a BRCA1 deletion and the need for heightened surveillance in adulthood. As BRCA1 genetic testing is traditionally performed on adult patients with informed consent, this case report highlights the need for ongoing conversations and research in the management of incidental fetal diagnosis discovered during routine prenatal testing, as well as the care and counseling of these patients and their families.