Skip Navigation
Genetics Home Reference: your guide to understanding genetic conditions About   Site Map   Contact Us
Home A service of the U.S. National Library of Medicine®
0-9 | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q-R | S | T | U | V | W | X | Y-Z



  • familial alobar holoprosencephaly
  • holoprosencephaly sequence
  • HPEC
  • HPE, familial
  • HPE - holoprosencephaly


Anterior midline brain, cranial, and facial malformations resulting from the failure of the embryonic prosencephalon to undergo segmentation and cleavage. Alobar prosencephaly is the most severe form and features anophthalmia; cyclopia; severe mental retardation; cleft lip; cleft palate; seizures; and microcephaly. Semilobar holoprosencephaly is characterized by hypotelorism, microphthalmia, coloboma, nasal malformations, and variable degrees of mental retardation. Lobar holoprosencephaly is associated with mild (or absent) facial malformations and intellectual abilities that range from mild mental retardation to normal. Holoprosencephaly is associated with chromosome abnormalities.

Definition from: MeSH via Unified Medical Language SystemThis link leads to a site outside Genetics Home Reference. at the National Library of Medicine

Holoprosencephaly is a developmental disorder that results when the forebrain of the embryo fails to divide and form the right and left halves of the brain. The disorder produces a single-lobed brain structure and severe skull and facial abnormalities. Often the deformities cause babies to die before birth. In mild cases, babies are born with near-normal brain development and facial abnormalities involving cleft lip or cleft palate.

Definition from: Talking Glossary of Genetic TermsThis link leads to a site outside Genetics Home Reference. from the National Human Genome Research Institute

See also Understanding Medical Terminology.

Published: February 1, 2016