Holoprosencephaly is a congenital defect of the central nervous system characterized by an incomplete or absent division of the embryonic forebrain – prosencephalon into distinct lateral cerebral hemispheres. This malformation arises during early embryogenesis and is frequently associated with specific craniofacial abnormalities. Based on the cardinal morphologic features the malformation is categorized into 3 main types – alobar, semilobar, lobar form and a special subtype MIV (middle interhemispheric fusion variant). The authors of the article present a case report of 2 children with alobar type of holoprosencephaly. They demonstrate a clinical course, examinations, complications and autopsy findings. Finally, they describe a classification, etiopathogenesis, morphology and clinical details of this malformation.

        Key words: alobar, semilobar, lobar holoprosencephaly, congenital CNS malformations