BackgroundWe report the occurrence of a severe pulmonary hypertension (PH) in a neonate affected by a left congenital diaphragmatic hernia (CDH). PH in this patient was associated with an abnormal origin of the right pulmonary artery from the right brachiocephalic artery. This malformation, sometimes named hemitruncus arteriosus, has to the best of our knowledge never been reported in association with a CDH.Case presentationA male newborn was hospitalized from birth in the neonatal intensive care unit after prenatal diagnosis of a left CDH. Ultrasound examination at 34 weeks of gestational age evaluated the observed-to-expected lung-to-head ratio at 49%. Birth occurred at 38+ 5weeks of gestational age. Soon after admission, severe hypoxemia, i.e., preductal pulse oximetry oxygen saturation (SpO2) < 80%, prompted therapeutic escalation including the use of high frequency oscillatory ventilation with fraction of inspired oxygen (FiO2) 100% and inhaled nitric oxide (iNO). Echocardiography assessment revealed signs of severe PH and normal right ventricle function. Despite administration of epoprostenolol, milrinone, norepinephrine, and fluid loadings with albumin and 0.9% saline, hypoxemia remained severe, preductal SpO2inconsistently greater than or equal to 80-85% and post ductal SpO2lower on average by 15 points. This clinical status remained unchanged during the first 7 days of life. The infant’s clinical instability was incompatible with surgical intervention, while chest X-ray showed a relatively preserved lung volume, especially on the right side. This prompted an additional echocardiography, aimed at searching an explanation of this unusual evolution and found an abnormal origin of the right pulmonary artery, which was confirmed on computed tomography angiography subsequently. A change in the medical strategy was decided, with the suspension of pulmonary vasodilator treatments, the administration of diuretics, and the decrease in norepinephrine dose to decrease the systemic-to-pulmonary shunt. Progressive improvement in the infant respiratory and hemodynamic status enabled to perform CDH surgical repair 2 weeks after birth.ConclusionsThis case recalls the interest of systematic analysis of all potential causes of PH in a neonate with CDH, a condition frequently associated with various congenital malformations.