SFTPD and bacterial pneumonia: The number of patients with high fever and sore throat in the bacterial pneumonia group were significantly higher than those in the AE-IIPs group (p = 0.027 and p = 0.008, respectively).Although there was no significant difference in the serum WBC counts, serum KL-6, SP-D, and D-dimer levels in patients with AE-IIPs were significantly higher than those with pneumonia superimposed on CF-IIPs.