The most severe type of holoprosencephaly, the forebrain is not completely divided, characterized by the fusion of the two cerebral hemispheres and the absence of the interhemispheric fissure.
Other associated symptoms may be cyclopia, proboscis or hypotelorism
Malformations of the heart, intestines, or brachial plexus injury (myelomeningocele) may occur in other organs of the body.