Alobar holoprosencephaly in one of twin neonates

Holoprosencephaly (HPE) is a congenital structural anomaly of the forebrain which is often diagnosed prenatally, usually in singleton pregnancies. This is a case of alobar HPE affecting one of 19-day-old twin neonates which was only detected postnatally. The other twin was unaffected. The anomaly was not diagnosed in utero because a prenatal sonogram was not performed. This case is presented to reemphasize the need for thorough routine prenatal/obstetrics sonography. After birth, transfontanelle ultrasonography is a useful imaging modality for diagnosing this debilitating cerebral structural anomaly, but definitive classification requires cross-sectional brain imaging with computed tomography or magnetic resonance imaging.