SFTPD and interstitial lung disease: At the onset of AE-ILD, although the median serum lactate dehydrogenase level was significantly lower in the N group than that in the No-N group, the serum markers associated with AE-ILD, including the Krebs von den Lungen-6, surfactant protein D, white blood cell count, and C-reactive protein levels, did not differ significantly between the groups.