question: What is holoprosencephaly?
answer: Holoprosencephaly (HPE) is a congenital defect of the brain, median structures, and face resulting from an incomplete cleavage of the primitive brain during early embryogenesis . The most common developmental defect is characterized by inadequate or absent midline division of the forebrain into cerebral hemispheres with concomitant midline facial defects in the majority of cases .