SFTPD and acute respiratory distress syndrome: Considering that pulmonary fibrosis is also a late complication of ARDS, in the acute stage of ARDS, there is a significant increase in SP-D levels attributed to disruption of the air-blood barrier, and excessive proliferation of type II alveolar cells observed in the proliferative stage of ARDS may subsequently result in an overproduction of SP-D (36).