Agnathia literally means absence or severe dysplasia of the mandible. It is a rare expression of first branchial arch malformation therefore, only 100 case have been reported so far. Some of these cases were syndromic, occurring with patterns of associated anomalies. The fetus of our case had been in polyhydramnios, and proved to have mandibular dysplasia with prenatal ultrasound diagnosis at 31 weeks of gestation. Ninety minutes after delivery, this female infant died due to severe respiratory failure. The facial features included agnathia, severe microstomia, low set ears and bird face. The mandible was absent with ordinary X-ray and computed tomography. Chromosomal examination revealed normal karyotype (46XX). The autopsy findings were microglossia, cleft palate, hypoplasia of the cerebellum and congestion of the lung. There are many reports about complicated variation of holoprosencephalyagnathia. In our case, since the separation-formation of telencephalon was normally recognized with X-ray CT, we diagnosed it as agnathia not associated with holoprosencephaly-agnathia.
