Holoprosencephaly is a disorder caused by the failure of the prosencephalon (the embryonic forebrain) to sufficiently divide into the double lobes of the cerebral hemispheres. The result is a single-lobed brain structure and severe skull and facial defects. In most cases of holoprosencephaly, the malformations are so severe that babies die before birth. In less severe cases, babies are born with normal or near-normal brain development and facial deformities that may affect the eyes, nose, and upper lip.
There are three classifications of holoprosencephaly. Alobar, in which the brain has not divided at all, is usually associated with severe facial deformities. Semilobar, in which the brain's hemispheres have somewhat divided, causes an intermediate form of the disorder. Lobar, in which there is considerable evidence of separate brain hemispheres, is the least severe form. In some cases of lobar holoprosencephaly the baby's brain may be nearly normal.
The least severe of the facial anomalies is the median cleft lip (premaxillary agenesis). The most severe is cyclopia, an abnormality characterized by a single eye located in the area normally occupied by the root of the nose, and a missing nose or a proboscis (a tubular-shaped nose) located above the eye. The least common facial anomaly is ethmocephaly, in which a proboscis separates closely-set eyes. Cebocephaly, another facial anomaly, is characterized by a small, flattened nose with a single nostril situated below incomplete or underdeveloped closely-set eyes.
Carter Centers for Brain Research in Holoprosencephaly c/o Texas Scottish Rite Hospital P.O. Box 190567 2222 Welborn Street Dallas, TX 75219-9982 hpe@tsrh.org http://www.carterdatabase.org/hpe/ Tel: 214-559-8411 Fax: 214-559-8383 |
National Organization for Rare Disorders (NORD) 55 Kenosia Avenue Danbury, CT 06810 orphan@rarediseases.org http://www.rarediseases.org Tel: 203-744-0100 Voice Mail 800-999-NORD (6673) Fax: 203-798-2291 |
The Arc of the United States 1825 K Street, NW Suite 1200 Washington, DC 20006 Info@thearc.org http://www.thearc.org Tel: 202-534-3700 800-433-5255 Fax: 202-534-3731 |
March of Dimes 1275 Mamaroneck Avenue White Plains, NY 10605 askus@marchofdimes.com http://www.marchofdimes.com Tel: 914-997-4488 888-MODIMES (663-4637) Fax: 914-428-8203 |
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Last updated February 13, 2007