Table 1.

Proposed classification of paediatric PAP

Category of disease	Exemplar conditions
Disorders of surfactant protein metabolism	SFTPB, STFPC, ABCA3 and TTF1 mutations
GM-CSF receptor gene mutations	α- and β-chain mutations
Other genetic disorders	MARS, STING, COPA and GATA2 mutations
Metabolic disease	Lysinuric protein intolerance, Niemann–Pick disease
Associated with immune deficiency
Congenital	SCID, ADA deficiency
Acquired	HIV, leukaemia
Associated with connective tissue disease	Idiopathic juvenile chronic arthritis
Miscellaneous	Congenital heart disease
Diseases seen in adults
Exclusively in adults	Macrophage blockade, lymphoma
Mainly in adults	Autoimmune

GM-CSF: granulocyte–macrophage colony-stimulating factor; STFPB: surfactant protein B; STFPC: surfactant protein C; ABCA3: ATP-binding cassette 3; TTF1: thyroid transcription factor 1; MARS: methionyl transfer RNA synthetase; STING: stimulator of interferon; COPA: non-clathrin-coated vesicular coat protein A; GATA2: GATA-binding protein 2; SCID: severe combined immunodeficiency; ADA: adenosine deaminase.