Because at clinical diagnosis of the patient, both the exact cause of the PAP and effective treatments in small children were unknown, empirical high dose glucocorticosteroids in pulses were used ( Figure 2A ) and under the impression that they might be helpful, systemic corticosteroids were used for prolonged periods until the age of 7.5 years. During this time, azathioprine as a steroid saving agent was also used without any apparent benefit. However, we clearly observed that severe infectious complications were only observed during the time of increased immunosuppression by these agents (Figure 2A, B) . At 5 years of age an Aspergillus fumigatus infection with formation of a cavity, leading to severe cardio-respiratory failure and resuscitation followed by resection of the left lower lobe ( Figure 2B , Figure 5A -D). At age 7.5 years she suffered a pulmonary para-influenza infection, leading to ARDS and necessitating mechanical ventilation. Additionally, the child had many mild respiratory exacerbations, mostly believed to be induced by viral upper-and lower respiratory tract infections. Figure 4 At age 5 y, during four consecutive whole lung lavage sessions perfluorocarbon (PFC) was instilled into the lungs after the 6th, 7th, or 8th of the 500 ml wash in order to enhance the recovery of surfactant material. The concentration of phosphoplipids (and total protein (not shown)) washed out was not significantly altered compared to lavages done at that age without PFC ( Figure. 4 A, B) . From age 3 to 4 1/2 years therapy with inhaled and subcutaneous injections of recombinant GM-CSF was done (see also Figure. 2 B). Although the intervals between consecutive therapeutic whole lung lavages were increased with GM-CSF treatment the amount of protein removed was also increased, demonstrating no reduction of protein amount with GM-CSF treatment ( Figure. 4 C, D) . Note that not all lavages were available for total protein measurements.