The most common defect of the forebrain is holoprosencephaly (HPE), characterized by absence in the forebrain division. Holoprosencephaly has a prevalence of 1 / 10,000 in newborns; the cyclopia of 1 / 100,000 births and the agnathia, in a series of cases of holoprosencephaly ranges from 0.8 to 10 %. The objective was the description of the morphological and histopathological characteristics of fetus with holoprosencephaly and its associated malformations. A male fetus was studied. Microdissection was performed under the stereomicroscope, taking microphotographs with AxioCam camera and AxioVision 4.8 soft- ware, and histopathological study. The estimated gestational age was 12.4-13.2 weeks, the findings were semilobar HPE, associated with cyclopia, hypoplastic oral outline without buccal opening, covered by a membrane and lips absence. The histopathological study reported: eye with lens, retina and cornea only; in the face, proboscis with tubular cartilage in formation associated with mesenchyme and musculoskeletal sheath, and small oral cavity, delimited by hypoplastic mandible conformed by cartilage. The literature is reviewed and reaffirmed the need for multidisciplinary studies of this disease to improve their understanding.
KEY WORDS: Semilobar holoprosencephaly; Dysgnathia complex; Cyclopia, prosencephalon; Gastrulation.