BACKGROUND We present a report of a rare cardiac malformation case as well as a review of the literature. In addition, the diagnostic features are discussed. CASE REPORT The case of a female newborn who died on her third day of life was studied at the Institute of Legal Medicine, University of Chieti-Pescara (Italy). The investigations around her death revealed a cardiac congenital malformation, seen as a rare variant of a common arterial trunk, in which the aorta was fused with the right branch of the pulmonary artery. The ascending aorta showed hypoplasia, while the coronary arteries were free of any pathological findings. The atrial septum showed a closed foramen ovale and the ventricular septum did not show any defect. Only an isolated right ventricular hypertrophy and dilation with no other cardiac abnormalities was found. The cause of death was acute respiratory failure on the third day of extrauterine life when the ductus Botalli closed. The karyotype analysis performed in this case was normal, and the fluorescent in situ hybridization analysis did not show the 22q11.2 microdeletion suggestive of the DiGeorge syndrome. CONCLUSIONS These findings underline the value of 3-dimensional/4-dimensional ultrasound imaging when added to a fetal cardiology screening program, and the need for improvements in postnatal screening routines by using pulse oximetry in order to discover isolated vascular defects before circulatory collapse occurs, as well as to reduce the medico-legal disputes in cases of missed diagnosis. We found the relevant literature search lacked a description of this congenital malformation, which supports our deeper perinatal investigation.