SFTPD and COVID-19: The objective of this study was to investigate the association between a specific single-nucleotide polymorphism (SNP) in the SP-D gene, designated as rs721917 (C/T Met31Thr), and its potential impact on susceptibility to and severity of COVID-19.<h4>Methods</h4>This retrospective case-control study enrolled 135 participants, including 111 confirmed COVID-19 patients and 24 asymptomatic or presymptomatic individuals, who were classified into five subgroups.