At age 12 years (in 2009) analysis of the patient's CSF2RA gene revealed the homozygous Ser25X stop-mutation in exon 3 resulting in the almost complete absence of the GM-CSF receptor alpha chain and causing the alveolar proteinosis we observed ( Figure 6A ). The parents were heterozygous for the mutation (Figure 6A, B) . Mutations in SFTPC, SFTPB and ABCA3 were excluded.