NKX2-1 and pulmonary alveolar proteinosis: Mutations in the genes for surfactant protein deficiency including SFTPB (surfactant protein-B), SFTPC (surfactant protein-C), ABCA3 (ATP binding cassette subfamily A member 3)6, and NKX2-1 (thyroid transcription factor 1)7 lead to PAP with diffuse lung disease.