Surfactant protein B deficiency: Insights into surfactant function throughclinical surfactant protein deficiency

Surfactant protein B (SP-B) deficiency is a disorder of surfactant function with complete or transient absence of SP-B in term neonates. SP-B, 1 of 4 described surfactant-associated proteins, plays a key role in surfactant me tabolism, particularly in intracellular packaging of surfactant components, formation of tubular myelin, and the presentation of the surfactant phosph olipid monolayer to the air-fluid interface within the alveolus. Neonates w ith clinical SP-B deficiency best demonstrate the key role of SP-B in surfa ctant function. "Classic" deficiency results in severe respiratory failure in term infants and death unless lung transplantation is performed. Because the initial description of complete deficiency secondary to a homozygous f rameshift mutation in codon 121 of the SP-B cDNA, partial deficiencies with differing genetic backgrounds and less severe clinical courses have been r eported. These partial deficiency states may provide a clearer picture of g enotype/phenotype relationships in SP-B function and surfactant metabolism. SP-B deficiency or dysfunction may be more common than once thought and ma y play a significant role in neonatal lung disease.