Persistent pulmonary hypertension of the newborn associated with excessive pulmonary arterial muscularization: report of an autopsy case.

A 3700-g male infant born at 37 weeks' gestation presented with cyanosis at birth. He was diagnosed as having persistent pulmonary hypertension of the newborn (PPHN) on the basis of persistent hypoxemia, despite continuous mechanical ventilatory support with 100% O2, and right-to-left shunting through the foramen ovale shown by Doppler echocardiography. Treatment with hyperventilation, and administration of tolazoline, prostaglandin E1 and MgSO4 failed to reverse his hypoxemia. High ventilator settings were required, and pneumothoraces ensued. Airway resistance increased gradually with development of hypercapnia and deterioration of hypoxemia. Bradycardia unresponsive to resuscitation occurred, and he died at eight days of age. Postmortem examination of the lungs revealed increased peripheral connective tissue and diffuse extension of medial smooth muscle to the precapillary pulmonary arteries. Excessive antenatal muscularization of the peripheral pulmonary arteries and resultant increased vasoconstriction capacity may have played an important role in the pathogenesis of PPHN in this case.