Pulmonary hypertension in connective tissue diseases: epidemiology, pathogenesis, and treatment

Pulmonary hypertension (PH) is a clinical condition characterized by increased pulmonary arterial pressure arising from a heterogeneous range of diseases that has a deteriorating effect on the quality of life and may cause early mortality if left untreated. Connective tissue disorders (CTD)-associated PH is the second most common cause of pulmonary arterial hypertension (PAH), after the idiopathic form, categorized as group I. Systemic scleroderma (SSc) accounts for 75% of CTD-associated PH cases. Although SSc ranks first place for CTD-associated PH, SSc is followed by systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD), having a lesser frequency of PH occurrence, while it occurs as a rare complication in cases with rheumatoid arthritis (RA) and inflammatory myositis. PH may also occur during non-SSc CTDs and even other rheumatic diseases, including Behcet's disease and adult-onset Still's disease, albeit to a lesser extent. The prognosis of CTD-associated PH is worse than the other forms of PH. Although, as in idiopathic pulmonary arterial hypertension (IPAH), the mechanism of CTD-related PH is associated with an increase in vasoconstrictors like endothelin-1 and a decrease in vasodilators like prostacyclin and nitric oxide production, inflammation, and autoimmune mechanisms also play a role in the development and progression of PH. This may lead to the involvement of more than one mechanism in CTD-associated PH. Knowing which mechanism is dominant is very important in determining the treatment option. This review will primarily focus on the epidemiology, risk factors, and prognosis of PH that develops during rheumatic diseases; the pathogenesis and treatment will be briefly mentioned in light of the newly published guidelines. Key Points • Pulmonary arterial hypertension (PAH) associated with connective tissue disease (CTD) in Western countries is the second most common type of PAH after idiopathic PAH (IPAH). • CTD-PH can be seen most often in systemic scleroderma (SSc), less in systemic lupus erythematosus (SLE), mixed CTD (MCTD), and rarely in other CTDs. • While current guidelines recommend annual transthoracic echocardiography as a screening test for asymptomatic SSc patients, screening for PH is not advised in the absence of symptoms suggestive of PH in other CTDs. • CTD-PH treatment can be divided into specific vasodilator PH treatments and immunosuppressive therapy. Current treatment guidelines recommend the same treatment algorithm for patients with CTD-associated PH as for patients with IPAH. Several case series have shown the beneficial effect of immunosuppressive agents in patients with SLE-PH and MCTD-PH.