[Holoprosencephaly: pathogenesis, phenotypic characteristics. About four cases].

Holoprosencephaly is a rare brain abnormality resulting from an incomplete cleavage of the primitive prosencephalon of forebrain during early embryogenesis. It includes a series of rare complex and heterogenosis disorders. Alobar form is associated with an extremely poor fetal prognosis. Here we report three cases of alobar holoprosencephaly and one case of semilobar holoprosencephaly diagnosed at the third trimester. Causes, diagnosis and management of holoprosencephaly are discussed referring to literature.