SFTPD and pulmonary emphysema: A similar emphysema-like symptom has been reported in Sp-D−/− mice; namely, targeted disruption of the Sp-D gene has been shown to cause the accumulation of surfactants, increase in the number of lipid-laden foamy macrophages, and emphysema, which was associated with increased production of matrix metalloproteinases [15], [26].