Stage	Chest radiograph characteristics	Frequency (%)	Rates of spontaneous remission (%)
0	Normal	5 to 10	—
I	BHL	50	55 to 90
II	BHL and parenchymal infiltrates	25	40 to 70
III	Parenchymal infiltrates without BHL	15	10 to 20
IV	Signs of fibrosis	5 to 10	0 to 5