Several studies suggested the presence of allelic variations of SP-D SNP rs721917 in different diseases, indicating that both variants may facilitate disease onset, such as allergic rhinitis (Thr11) [96], coronary stenosis (Thr11) [97], COPD (Thr11) [98], COPD (Met11) [39], type II diabetes (Met11) [99], lung cancer (Thr11) [100], rheumatoid arthritis (Thr11) [101], tuberculosis (Thr11) [102], atherosclerosis (Thr11) [53], cystic fibrosis (Thr11) [103], and multi-organ dysfunction syndrome (Thr11) [104]. Here, SFTPD is linked to chronic obstructive pulmonary disease.