[Pulmonary arterial hypertension and systemic diseases].

Certain system diseases which include vascular involvement may be accompanied by pulmonary artery hypertension (PAHT). This chiefly concerns connective tissue disorders, notably scleroderma, CREST syndrome and mixed connective tissue disease and, to a lesser extent, systemic lupus erythematosus. The onset of PAHT in relation to vasculitis of the great vessels or necrosing angeitis is rare. It may result from pulmonary artery vasoconstriction of hypoxic origin during diffuse interstitial pulmonary fibrosis, a thrombo-embolic mechanism, a vasomotor phenomenon equivalent at pulmonary level to Raynaud's syndrome, and above all from pulmonary vasculitis, the commonest mechanism. The incidence of PAHT is such connective tissue disease is probably underestimated since it is a complication often unrecognised clinically. It is a major cause of death in such conditions, certain of which nevertheless enjoy a benign reputation. With the exception of rare cases of favourable outcomes under the influence of corticosteroids and immunosuppressants in cases of mixed connective tissue disease, no treatment has in fact been shown to be effective in terms of survival.