SFTPC and chronic obstructive pulmonary disease: The common non-synonymous variants in SFTPC (p.T138N and p.S186N) and SFTPA2 (p.A91P) were present in similar frequencies in the IPF and COPD cohorts compared to the general population, as were the common synonymous variants in ABCA3 (p.F353F, p.P585P and p.S1372S) (see online supplementary table S1).