Antenatal Ultrasonographic Diagnosis of a Constellation of Alobar Holoprosencephaly, Ethmocephaly, and Hydronephrosis in a Case of Early-Onset Intrauterine Growth Retardation: A Case Report.

Alobar holoprosencephaly is a congenital malformation that results from failure of the forebrain/prosencephalon to divide into right and left halves. Despite the literature on the genetic and chromosomal abnormalities associated with this condition, information on additional causes and explanations for variability in phenotypic expressivity are lacking. We report a case of early-onset intrauterine growth retardation with alobar holoprosencephaly, ethmocephaly, and hydronephrosis diagnosed on antenatal ultrasonography in a 27-year-old primigravida with no known risk factors or family history. The combination of holoprosencephaly with associated midline facial anomalies and the genitourinary abnormality, in this case, constitutes a rare phenotypic presentation. This case emphasizes the importance of antenatal ultrasonography in the early detection of lethal anomalies like alobar holoprosencephaly. The pregnancy was safely terminated in accordance with the mother's decision.