Pulmonary surfactant-associated protein B (SFTPB), amongst other roles, is a component of surfactant, a surface-active film that helps reduce surface tension in alveoli. Defects in the SFTPB gene result in loss-of-function SFTPB proteins and accumulation of partially-processed , inactive pro-SFTPC in alveoli. Defects in SFTPB can cause pulmonary surfactant metabolism dysfunction 1 (SMDP1; MIM:265120), a rare lung disorder due to impaired surfactant homeostasis characterised by alveoli filling with floccular material. Excessive lipoprotein accumulation in the alveoli results in a form of respiratory distress syndrome in premature infants (RDS; MIM:267450) (Vorbroker et al. 1995, Li et al. 2004, Wert et al. 2009, Whitsett et al. 2015).