Pulmonary hypertension in rheumatic diseases

Pulmonary hypertension (PH) is a progressive disease of the pulmonary vasculature characterized by increased vascular resistance and pressure overload of the right ventricle. Histologically, PH lungs demonstrate medial hypertrophy of small pulmonary arteries and proliferation of endothelial cells resulting in plexiform lesions. Recent studies have identified mutations of the bone morphogenetic protein receptor 2 (BMPR2) gene and the activin-receptor-like kinase 1 (ALK1) gene, that affect the transforming growth factor beta (TGF-beta) receptor superfamily, a group of transmembrane signaling molecules with serine-threonine kinase activity that are involved in the regulation of cell growth. Several lines of evidence indicate that the development of PH is a multi-hit process, where one of the events is having a. gene mutation and another might be a circumstantial condition or other disease-modifying genes. It is unknown which mechanism that is critical in rheumatic diseases causes pulmonary vascular disease. PH is most frequently associated with systemic sclerosis (SS), systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD), however, it is still a rare manifestation of these disorders. For example, approximately 10% of SS cases manifest pulmonary vascular disease. In recent years symptomatic vasodilator therapies have been employed and have been able to improve exercise capacity and survival in these patients.