• Pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare disease in adults, with an estimated prevalence of approximately 30–50 per million.1 2 It is even less frequent in children, with an estimated prevalence of approximately 10–20 per million.3 PAH includes idiopathic PAH (IPAH), hereditable PAH and associated PAH, for example PAH associated with connective tissue diseases, congenital heart disease, HIV, portal hypertension or toxins/drugs. PAH is a disease of progressive increases in pulmonary vascular resistance and pulmonary arterial pressure that, if untreated, results in death within 2–3 years in adults and within 1 year after diagnosis in children with IPAH, ie, a horrific outcome for a disorder entirely limited to the pulmonary vasculature.4 Not surprisingly, because of its rarity, it has been extremely difficult to study the disease to gain an understanding of its pathobiology; an essential step to develop safe and effective therapies.

Based on observational data demonstrating that overall, PAH in children is far more similar than different compared with PAH in adults, we have extrapolated what we have learned from the adult PAH arena to children. In both children and in adults, the disease presents with a broad spectrum of clinical features that are manifestations of similar pathological and pathobiological processes. The histopathological lesions seen in adults are also observed in children. Both populations have endothelial dysfunction with abnormalities in vascular and endothelial homeostasis. A comparable genetic background is observed in adults and in children. Based on these observations, consensus in the paediatric pulmonary hypertension community is to use similar diagnostic and therapeutic algorithms in paediatric (based on expert opinion) and adult (evidence-based) patients.5

Moledina et al6 report in this issue of Heart a 7-year retrospective experience in the UK with childhood IPAH (see page 1401). The cohort of 64 children is one of the largest …