Infantile pulmonary alveolar proteinosis with interstitial pneumonia: bilateral simultaneous lung lavage utilizing extracorporeal membrane oxygenation and steroid therapy

Therapeutic lung lavages in children and adults

Background

Pulmonary alveolar proteinosis (PAP) is a rare disease, characterized by excessive intra-alveolar accumulation of surfactant lipids and proteins. Therapeutic whole lung lavages are currently the principle therapeutic option in adults. Not much is known on the kinetics of the wash out process, especially in children.

Methods

In 4 pediatric and 6 adult PAP patients 45 therapeutic half lung lavages were investigated retrospectively. Total protein, protein concentration and, in one child with a surfactant protein C mutation, aberrant pro-SP-C protein, were determined during wash out.

Results

The removal of protein from the lungs followed an exponential decline and averaged for adult patients 2 – 20 g and <0.5 to 6 g for pediatric patients. The average protein concentration of consecutive portions was the same in all patient groups, however was elevated in pediatric patients when expressed per body weight. The amount of an aberrant pro-SP-C protein, which was present in one patient with a SP-C mutation, constantly decreased with ongoing lavage. Measuring the optical density of the lavage fluid obtained allowed to monitor the wash out process during the lavages at the bedside and to determine the termination of the lavage procedure at normal protein concentration.

Conclusion

Following therapeutic half lung lavages by biochemical variables may help to estimate the degree of alveolar filling with proteinaceous material and to improve the efficiency of the wash out, especially in children.

Pulmonary alveolar proteinosis in children

Pulmonary alveolar proteinosis (PAP) is a rare cause of chronic interstitial lung disease in children characterised by accumulation of a lipoproteinaceous material in the alveoli. Bronchoalveolar lavage is the key diagnostic tool, revealing a milky appearance of the return fluid and a periodic acid-Schiff staining material in the alveolar macrophages. PAP is a heterogeneous disease. Immediate-onset forms leading to early and fatal respiratory failure may be related to SP-B deficiency. Postnatal-onset PAP may be associated with various diseases or may be primary. The latter has a polymorphic progression from asymptomatic to uncontrollable respiratory failure. Recent studies have implicated GM-CSF and/or its receptor but the exact underlying mechanisms are still unknown. Therapeutic lung lavages are the only effective treatment for severe cases.

Pulmonary alveolar proteinosis: progress in the first 44 years

Pulmonary alveolar proteinosis is a rare clinical syndrome that was first described in 1958. Subsequently, over 240 case reports and small series have described at least 410 cases in the literature. Characterized by the alveolar accumulation of surfactant components with minimal interstitial inflammation or fibrosis, pulmonary alveolar proteinosis has a variable clinical course ranging from spontaneous resolution to death with pneumonia or respiratory failure. The most effective proven treatment--whole lung lavage--was described soon after the first recognition of this disease. In the last 8 years, there has been rapid progress toward elucidation of the molecular mechanisms underlying both the congenital and acquired forms of pulmonary alveolar proteinosis, following serendipitous discoveries in gene-targeted mice lacking granulocyte-macrophage colony-stimulating factor (GM-CSF). Impairment of surfactant clearance by alveolar macrophages as a result of inhibition of the action of GM-CSF by blocking autoantibodies may underlie many acquired cases, whereas congenital disease is most commonly attributable to mutations in surfactant protein genes but may also be caused by GM-CSF receptor defects. Therapy with GM-CSF has shown promise in approximately half of those acquired cases treated, but it is unsuccessful in congenital forms of the disease, consistent with the known differences in disease pathogenesis.