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Emily Graves and Victoria Bonds

Where on chromosome is problem?

What is problem?

Holoprosencephaly (HPE) is a relatively common birth defect of the brain, which can also affect facial features, including closely spaced eyes, small head size, and sometimes clefts of the lip and the roof of the mouth, as well as other birth defects. 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 of a single-lobed brain structure and severe skull and facial defects. In most cases of holoproscencephaly, 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.
This birth defect occurs soon after conception and has its prevalence of 1 in 250 during early embryo development, and 1 in 10,000 to 1 in 20,000 at term.

There are three classifications of holoproscencephaly:
-Alobar, in which the brain has not divided at all, is usually associated with severe facial features.
-Semilobar, in which the brain's hemispheres have somewhat divided, causes an intermediate form of disorder.
-Lobar, in which there is considerable evidence of separate brain hemispheres, is the least severe form. In some cases of lobar holoproscencephaly, the baby's brain may be nearly normal.

The milder craniofacial characteristics of HPE include mid face flattening, closely spaced eyes, flat nasal bridge, and single maxillary central incisor. The least severe of the facial anomalies is the median cleft lip.
**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 which is a tubular-shaped nose located above the eye.

The cause of HPE in any individual family is often unknown.



What is the prognosis?

The prognosis for individuals with the disorder depends on the severity of the brain and facial malformation and associated clinical complications. HPE is not a condition in which the brain deteriorates over time. Although serious seizure disorders, autonomic dysfunction, complicated endocrine disorders and other life-threatening conditions may sometimes be associated with HPE, the mere presence of HPE doesn't mean that these serious problems will occur or develop over time without any previous indication or warning. These abnormalities are usually recognized shortly after birth or early in life and only occur if areas of the brain controlling those functions are fused, malformed, or absent.

Prognosis is dependent upon the degree of fusion and malformation of the brain, as well as other health complications that may be present.

Cite your sources



http://www.genome.gov/12512735#al-4