Bleeding and telangiectasia may reflect enhanced superficial angiogenesis and vascular fragility resulting from alterations in endothelial TGF-β/activin signalling, whereas thrombocytopenia is consistent with reduced activin-mediated support of megakaryocyte maturation, with higher rates observed in patients receiving parenteral prostacyclin (21.5% vs. 3.1%). The gene discussed is INHBE; the disease is Telangiectasia.