Holoprosencephaly is a brain development abnormality where the brain does not properly separate into the left and right hemispheres. This disorder also affects the development of the face as well as that of the head. Holoprosencephaly is categorized into four types with the level of severity being the distinguishing factor among the four classes.From the least to most severe they include middle interhemispheric variant (MIHV), lobar, semi-lobar, and Alobar. Generally, you can tell the severity of the brain defect judging by the degree of the severity of the facial defect. As such, individuals that are most severely affected by Holoprosencephaly feature one central eye – the condition is referred to as cyclopia – and a tubular nasal structure – referred to as proboscis – which is located above the eye.The less severe forms of these conditions feature a partially divided brain. The eyes are also set close together. Other common symptoms of Holoprosencephaly include pituitary gland disorders and intellectual disability. Holoprosencephaly can result from a mutation in any of some 14 different genes as well as chromosome abnormalities or teratogens (agents that cause birth defects). It could also be a subsequent consequence of various unique genetic syndromes.
