Pulmonary arterial hypertension (PAH) is the main cause of death among systemic sclerosis (SSc) patients, according to a recent Chinese cohort study. Researchers found SSc-related clinical features that associate with disease outcome, possibly helping future characterization of SSc.
The study, “Prognostic profile of systemic sclerosis: analysis of the clinical EUSTAR cohort in China” was published in the journal Arthritis Research & Therapy.
SSc is an autoimmune disease whose cause is not known. It manifests with different symptoms and varying severity among patients, making their outcomes highly diverse. Still, SSc can be divided into two main subtypes depending on the extent of skin involvement: limited cutaneous SSc and diffuse cutaneous SSc. The two subtypes differ in prognostic outcomes.
Yet, while prognosis is mainly influenced by SSc subtype, disease development may be influenced by demographic features, such as a patient’s ethnicity or residency.
To better understand SSc progression and improve disease management, researchers at Peking Union Medical College Hospital (PUMCH) investigated risk factors and causes of death associated with SSc.
The team followed outpatient visits of SSc patients diagnosed between February 2009 and December 2015. They used health records from the European Scleroderma Trials and Research group (EUSTAR) and Chinese Rheumatism Data Center (CRDC) databases to establish links between SSc features and clinical outcomes.
In total, 448 SSc patients were analyzed. Most were women (90.4%), had an average age of 42.8 years at diagnosis, and had different SSc subtypes — 56.7% had limited cutaneous and 43.3% diffused cutaneous SSc. Patients were followed at intervals of 6-12 months for a median duration of 4.5 years.
During the course of the study, 40 patients died. The main cause of death was found to be SSc-related complications (27 deaths), most notably lung involvement.
Further comparison of clinical features in SSc patients showed that PAH and arrhythmia were significant independent risk factors of a poor prognosis. Researchers also found that PAH was the main cause of death, responsible for 55% of all SSc-related deaths.
Although previous reports have shown interstitial lung disease (ILD) to be an independent risk factor of poor outcome in SSc patients, the present study did not find such association. This is also reflected by the low death incidence caused by ILD, where only one out of 40 SSc patients died of the condition.
Researchers note, however, that 17 of 22 SSc patients who died because of PAH also had ILD, making it hard to establish the actual cause of death.
Treatment — especially with immune suppressants — was also associated with clinical outcome. The team found a protective effect against mortality among patients taking the herbal Chinese traditional medicine tripterygium wilfordii Hook F (TwHF) or the immune-suppressant medicine methotrexate (MTX). In contrast, they found that patients taking immune-suppresant cyclophosphamide (CTX) had a poorer prognosis.
Because of the different prognostic features of SSc subtypes, researchers also explored survival differences between limited and diffuse cutaneous SSc. However, they found no significant difference between the two subtypes regarding survival rates.
Overall, the team concluded that “PAH and arrhythmia at baseline are independent prognostic factors, whereas PAH instead of ILD is the leading cause of death in patients with SSc.”
The team believes that “the results from this and future studies should help elucidate the influence of various ethnic differences on SSc disease phenotype and prognosis,” and emphasized that further studies are needed to investigate the Chinese traditional medicine TwHF “as a protective factor for survival.”