A long-term observational study on autoimmune pulmonary alveolar proteinosis revealed a sustained and generalized decrease in serum autoantibody levels.

BACKGROUNDS AND

OBJECTIVES

Autoimmune pulmonary alveolar proteinosis (aPAP) is a rare lung disorder, and its long-term clinical outcomes, underlying determinants, and temporal dynamics of serum autoantibody levels remain poorly characterized.

METHODS

This single-center retrospective observational study comprised 64 patients diagnosed with aPAP, all of whom had been monitored for a minimum of three years following disease onset. Clinical courses were evaluated using disease severity score (DSS), based on arterial oxygen tension and respiratory symptoms. Serum anti–granulocyte-macrophage colony-stimulating factor (GM-CSF) IgG autoantibody (αGM) levels were quantified by enzyme-linked immunosorbent assay.

RESULTS

Among 64 patients with any DSS, 45.3% showed clinical improvement, 40.6% remained stable, and 14.1% experienced deterioration over median follow-up period of 7.8 years. In a binary logistic regression analysis excluding patients with an initial DSS of 1, for whom improvement was not feasible, higher initial DSS, higher baseline % forced vital capacity, and the absence of fibrotic patterns on computed tomography were identified as significant explanatory variables associated with DSS improvement, whereas whole lung lavage (WLL) and GM-CSF inhalation were not in the comparison of the initial and final DSS. Longitudinal assessment of serum αGM levels in 52 patients revealed a decline in 98% of them (n = 51) with an estimated antibody half-life of 3.5 years. GM-CSF inhalation therapy was significantly associated with lower final antibody levels adjusted for initial level and the interval between the initial and final measurements by analysis of covariance.

CONCLUSIONS

The overall decline in αGM levels observed in this study may suggest a favorable or stable long-term prognosis in aPAP; however, further longitudinal investigations are warranted to confirm this presumed association.