Surfactant metabolism dysfunction, pulmonary, 3 (SMDP3) is an autosomal recessive disorder characterized by failure to thrive, severe respiratory distress, tachypnea and surfactant deficiency.  The initial clinical presentation is usually severe, and starts during the first year of life.  However, onset of the condition may sometimes be delayed and the presentation may be later in infancy or childhood. 

Diagnosis of the condition is done through chest radiography that shows granular, hazy, ground-glass interstitial opacifications in patients’ lungs.  Most infants affected with the severe form of the disease die within the first months of life.  However, patients with the milder form of the condition can survive into childhood, adolescence or even adulthood.  The only curative treatment available is a lung transplant. 

Mutations in the ABCA3 gene cause SMDP3.  The encoded protein is expressed in alveolar type II pneumocytes and located in the limiting membrane of lamellar bodies.  It is critical for the synthesis of surfactants that help in reducing the surface tension of alveolar tissue and preventing lung collapse.

More than 200 mutations in the ABCA3 gene have been implicated in the development of interstitial lung disease.