Characteristics and risk factors of mortality in patients with systemic sclerosis-associated interstitial lung disease

Background Systemic sclerosis (SSc) is a heterogeneous autoimmune disease characterized by dysregulation of fibroblast function, which often involves the lungs. Interstitial lung disease (ILD) associated with SSc (SSc-ILD) is a major cause of death among patients with SSc. Our study aimed to identify risk factors for mortality and compare the clinical characteristics of patients with SSc-ILD. Patients and methods Patients were retrospectively enrolled between 2010 and 2018 in a tertiary hospital in Korea. Patients with SSc-ILD were classified depending on the first pulmonary function test or radiologic findings: extensive (n = 46, >20% disease extent on computed tomography (CT) or forced vital capacity [FVC] < 70% in indeterminate cases) and limited (n = 60, <20% disease extent on CT or FVC >= 70% in indeterminate cases). Results Patients in the extensive group were younger (mean age +/- SD 49.3 +/- 11.5) than those in the limited group (53.9 +/- 12.5, p = .067) at diagnosis. The extensive group showed frequent pulmonary hypertension (43.5% vs. 16.7%, p = .009) and higher erythrocyte sedimentation rate (61.3 +/- 33.7 vs. 42.1 +/- 26.0, p = .003) and mortality (32.6%, mean duration of follow-up, 100.0 +/- 44.7 months vs. 10.0%, 86.0 +/- 53.4 months, p = .011). ILD was detected within five years from the first visit (median years 3.5 (1.0, 6.0) vs. 4.5 (0.6, 9.0), survivors vs. non-survivors), and mortality occurred in 19.8% of all patients during a 15-year follow-up. Older age, lower FVC, and initial disease stage (limited or extensive) were associated with mortality, but FVC decline was similar in the limited and extensive groups, such as 15-20% in the first year and 8-10% in the next year, regardless of the initial extent of the disease. Conclusions Approximately 10% of patients with SSc-ILD in the limited and extensive group showed progression. ILD was detected at a median of less than five years from the first visit; therefore, it is necessary to carefully monitor patients' symptoms and signs from an early stage. Long-term surveillance is also required. Key messages Patients with systemic sclerosis-interstitial lung disease manifested a heterogeneous disease course. Approximately 10% of the patients in the limited group showed progression, which was similar to the proportion of patients in the extensive group. Interstitial lung disease was detected at a median of less than five years from the first visit.