Although it has been showed that increased serum surfactant protein D (SP-D) and Krebs von den Lungen-6 (KL-6) concentrations were associated with the decline of forced vital capacity (FVC) and the severity of interstitial pneumonia for patients with CTD-ILD [9–11], they have not been widely used in clinical practice. The gene discussed is SFTPD; the disease is interstitial lung disease.