Further data analyses from the ECLIPSE cohort have demonstrated that baseline serum SP-D levels are associated with baseline lung density and its decline over time (389); however, the correlation between SP-D and emphysema was recently challenged by observations of serum SP-D variation in smoking, pulmonary emphysema, and combined pulmonary fibrosis and emphysema (CPFE), where serum SP-D was clearly induced only in the CPFE group compared with the other groups (390). The gene discussed is SFTPD; the disease is combined pulmonary fibrosis-emphysema syndrome.