Clinical features of pulmonary arterial hypertension in young people with an ALK1 mutation and hereditary haemorrhagic telangiectasia

Background:Pulmonary arterial hypertension (PAH) has been linked to mutations in genes encoding two members of the transforming growth factor-β family, BMPR2 and ALK1, the latter of which is also associated with hereditary haemorrhagic telangiectasia (HHT). Relatively little is known about the genetics of childhood PAH, or about the clinical features of PAH in young patients with an ALK1 mutation.Methods and Results:Three individuals diagnosed with PAH at 4, 16 and 17 years of age were found on subsequent genetic screening to have non-synonymous mutations of ALK1. All probands met criteria for HHT, although two presented with PAH before HHT was diagnosed. Extended family history revealed relatives with HHT in all three kindreds, a presumptive family history of PAH in two, one with multiple family members dying from PAH at young ages. All three patients in this series had systemic or suprasystemic right ventricular pressure and significantly elevated pulmonary vascular resistance, initially not responsive to oxygen and/or inhaled nitric oxide. All patients had pulmonary arteriovenous malformations and systemic arterial desaturation.Conclusion:This report highlights ALK1 mutations associated with a variable PAH phenotype, including pulmonary arteriovenous malformations and severe PAH presenting early in life. Echocardiographic screening for elevated right ventricular pressure may be indicated in patients with HHT, particularly those with an identified ALK1 mutation. Clinical features or a family history of HHT should be elicited in children and adolescents with idiopathic PAH; ALK1 screening may be appropriate when such features are present.