Cyclopia in one of discordant twins: a case report.

Cyclopia is an uncommon congenital anomaly resulting from arrest of the development of the anterior end of the neural plate. It is always associated with abnormalities of the brain. Cyclopia has never been reported in one twin only. In this report, we describe a case of cyclopia in a female infant with normal karyotype who was one of discordant twins. The infant died perinatally. The parents were healthy and not sanguineously related. Prenatal imaging studies revealed cyclopia, holoprosencephaly and hypognathia. Postmortem examinations revealed one orbit, one eyeball and absence of the nose. The central nervous system included rudimentary cerebral hemispheres with fusion of the two lateral ventricles and the third ventricle forming a single large cavity. The superior aspect of each cerebral hemisphere consisted of only a transparent membrane. The olfactory bulb nad tract was absent. The optic nerves were not identified.