Mutations of activin-receptor-like kinase 1 (ALK-1) are not found in patients with pulmonary hypertension and underlying connective tissue disease.

Pulmonary arterial hypertension is a recognized clinical component of systemic autoimmune diseases, especially systemic sclerosis. Mutations in the bone morphogenetic protein receptor 2 gene reported in sporadic and familial primary pulmonary arterial hypertension have failed to be detected in patients with either scleroderma spectrum disease or underlying connective tissue diseases. Activin receptor-like kinase 1 (ALK-1) gene has recently been linked to the pathogenesis of pulmonary hypertension in patients with hereditary hemorrhagic telangiectasia, which has some resemblance with the CREST syndrome. The presence of mutations in the ALK-1 gene in ten patients with underlying connective tissue diseases was investigated.