Holoprosencephaly

Holoprosencephayly
* This composite image of Holoprosencephaly was created to help geneticists get a better analysis

What is Holoprosencephayly?

Holoprosencephaly is a rare brain abnormality in which the brain fails to divide into the right and left hemispheres, as it should. There are four types of the syndrome, identified by the severity of the abnormality. The more severe the brain abnormality, generally the more severe the unique facial features and symptoms will be.

What gene change causes Holoprosencephaly?

Some research suggests that up to 14 genes may be responsible for the syndrome. Another possible cause is attributed to what are called teratogens, or chromosomal abnormalities responsible for birth defects. Another possibility that it is the result of a combination of several unique genetic syndromes.

The exact mode of inheritance was unknown at the time this entry was recorded.

What are the main symptoms of Holoprosencephaly?

The symptoms are defined by the type of Holoprosencephaly identified.

Alobar holoprosencephaly: when both sides of the brain fail to divide at all. This is the most severe form of the syndrome. Individuals may develop just a single eye (cyclopia), absent eyes, eyes that are very close together or very small eyes. A tubular-shaped nose is also common with this form of the syndrome. A cleft lip that occurs in the middle of the face, or on both sides of the lip is another feature. Life expectancy with this type of the syndrome may vary, but generally, patients with this form of the syndrome are still born, die at birth, or rarely make it past six months.

Semi-lobar holoprosencephaly: when the left side of the brain fuses to the right side at the front and sides of the brain. Widely-spaced eyes, a flattened bridge and tip of the nose, one nostril, cleft palate and a cleft lip in the middle or both sides of the lip are unique facial features of the syndrome.
Lobar holoprosencephaly occurs when the brain divides into right and left ventricles, but the cerebral hemispheres remain fused at the front. Common features may include a bilateral cleft lip, closely spaced eyes, and a flattened nose. However, in some cases, no distinct facial abnormalities are evident.

Middle interhemispheric variant: when the brain fuses in the middle. Closely spaced eyes, a depressed and narrow nose may be present.

How is it diagnosed?

To find out if someone has a diagnosis of Holoprosencephaly, it is important to have a consultation and evaluation with a clinical genetic specialist.  Specialists may also suggest specific genetic testing or other types of tests to help reach a diagnosis.  FDNA’s AI technology can help speed up the diagnostic process by analyzing facial features and other health information.

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Holoprosencephayly
* This composite image of Holoprosencephaly was created to help geneticists get a better analysis

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