In general, mutations in the SP-B gene SFTPB are associated with fatal respiratory distress in the neonatal period, and mutations in the SP-C gene SFTPC are more commonly associated with interstitial lung disease in older infants, children, and adults.
However, unlike previous infants with hereditary SP-B deficiency, proSP-C was processed to the active SP-C peptide, suggesting that the defect in SP-B, rather than SP-C, caused the respiratory distress in this infant.