Atypical Causes of Severe Pulmonary Hypertension in Infancy.

Pulmonary hypertension (PH) is a progressive disease characterized by elevated pulmonary arterial pressure (PAP). It is defined for both adults and children as mean PAP exceeding 20 mmHg and pulmonary vascular resistance of at least 3 Woods Units (WU; indexed to body surface area in children).1 A more appropriate suggested definition of PH in infants is a ratio of pulmonary artery systolic pressure to the systemic arterial systolic pressure above 0.4.2 In addition, cardiac catheterization derived mean pulmonary artery pressures to mean systemic arterial pressure ratio >0.75 indicating severe pulmonary hypertension has been associated with worse outcome in children.1 PH can be life-threatening and often presents within hours after birth. Persistent PH of the newborn (persistent pulmonary hypertension of the newborn [PPHN]) is a common etiology of PH in infants, occurring in 0.4 to 6 per 1000 live births with increasingly higher frequency reported at earlier gestational ages.1,3,4 However, rare etiologies of pulmonary hypertension can go unrecognized and may present outside the neonatal period.5 We present 4 atypical cases of severe pulmonary hypertension and review how early recognition informed prognosis and guided timely intervention.