Abstract:

Cyclopia typically arises from incomplete separation of the embryonic eye primordia or developmental disorders in the midline forebrain, leading to fusion of the original visual vesicles on both sides towards the midline. It represents the most severe facial manifestation within the holoprosencephaly spectrum. Here, we present a case of stillbirth at 16 weeks of pregnancy with cyclopia. At 14⁺³ weeks gestation, fetal nuchal translucency examination revealed a significant fluid-filled dark area within the skull. Following termination of pregnancy, only one orbit and an accompanying frontal nasal column were discernible on the face of the fetus. Copy number variation sequencing (CNV-seq) analysis demonstrated chromosomal triploid variation along with chimeric duplication involving the X chromosome at a ratio approximately equal to 32%, accompanied by chimeric deletion affecting the Y chromosome at a ratio approximately equal to 32%. The etiology underlying cyclopia is heterogeneous and its pathogenesis remains elusive. Prenatal diagnosis and medical imaging play crucial roles in identifying monocular malformations during pregnancy, enabling timely termination when detected early, thereby minimizing physical and psychological harm to pregnant women while alleviating healthcare costs.

Key words: Eye abnormalities, Fetus, Ultrasonography, prenatal, Prenatal diagnosis, Triploid, Fetal death