Defective ABCA3 causes SMDP3

ATP-binding cassette sub-family A member 3 (ABCA3) is thought to play a role in the formation of pulmonary surfactant by transporting lipids such as cholesterol into lamellar bodies (LBs) in alveolar type II cells. In LBs, surfactant proteins and lipids are assembled into bilayer membranes that are secreted into the alveolar airspace, where they form a surface film at the air–liquid interface. Defects in ABCA3 can cause pulmonary surfactant metabolism dysfunction 3 (SMDP3), a usually fatal pulmonary disease in newborns, characterised by the absence of normal LBs and the presence of electron-dense inclusions within small vesicular structures. Loss of secretion of lipid pulmonary surfactants causes excessive lipoprotein accumulation in the alveoli resulting in severe respiratory distress.

Summary from Reactome (R-HSA-5683678), read 2026-09-23.