Elevation of IgG levels is a serological indicator for pulmonary fibrosis in systemic sclerosis with anti-topoisomerase I antibodies and those with anticentromere antibody.

It is unclear whether any clinical and laboratory features are associated with pulmonary fibrosis (PF) in systemic sclerosis (SSc). We assessed these features using a database of 29 patients with SSc and anti-topoisomerase I antibodies and 68 patients with SSc and anticentromere antibody (ACA). Clinical features were not associated with the incidence of PF in patients with SSc and anti-topoisomerase I antibodies, although severe skin sclerosis was correlated with the presence of PF in patients with ACA. Serum IgG levels were often raised in patients with SSc and PF. Serum IgG levels in patients with PF were significantly higher than those in patients without PF, and were negatively correlated with percentage vital capacity and percentage diffusing capacity of the lung for carbon monoxide. In addition, serum IgG levels were correlated with serum interleukin-6. Thus, serum IgG levels are associated with PF in patients with SSc and anti-topoisomerase I antibodies and in patients with SSc and ACA.