SSc patients with ILD had statistically significantly higher serum levels of IgG3 compared with the SSc patients without ILD [0.65 g/l (IQR 0.61–0.83 g/l) vs. 0.53 g/l (IQR 0.39–0.72 g/l), p < 0.05], and there was a slightly significant positive correlation between the percentage of ILD, assessed by CALIPER software at HRTC, and serum IgG3 (r = 0.305, p < 0.05). The gene discussed is IGHG3; the disease is systemic sclerosis.