SIGLEC9 and chronic obstructive pulmonary disease: Small-scale case–control studies investigating the possible correlations between the polymorphisms of SIGLEC genes and infectious disease susceptibility have revealed some correlations, such as SIGLEC14 null polymorphism and COPD exacerbation (102), pre-term delivery in the presence of GBS (63), Mycobacterium tuberculosis meningitis (138), and SIGLEC9 polymorphism and COPD exacerbation (133).