Haplotypes for each individual were inferred using PHASE statistical software (version 2.1) [21] . The haplotype of SFTPA1, SFTPA2 or the haplotype encompassing SFTPA1, SFTPA2 and SFTPD was ambiguous or could not be assigned in 12 individuals, who were excluded from the study. The order used for the haplotypes nomenclature is SFTPD-SFTPA1-SFTPA2. Linkage disequilibrium (LD) was measured by means of Arlequin (version 3.11) [22] and Haploview [23] softwares in the control group. In addition, pairwise LD between haplotypes of SFTPA1 and SFTPA2 as well as with the SFTPD SNP was characterized using Arlequin 3.11. The existence of LD was considered if D' >0.4.