Pulmonary alveolar proteinosis that improved after a COVID-19 infection: a case report.

Pulmonary alveolar proteinosis (PAP) is a rare disease caused by the accumulation of abnormal surfactant in the alveoli, leading to impaired gas exchange. A 54-year-old woman presented with intermittent wheezing who developed increasing infiltrates gradually on chest CT, was diagnosed with PAP in our department in December 2017. She then underwent granulocyte-macrophage colony-stimulating factor (GM-CSF) inhalation therapy for three months without improvement. Regular follow-up imaging and pulmonary function tests suggested disease progression. However, the patient declined whole-lung lavage (WLL) due to her unrestricted daily activities. Two months after a coronavirus disease 2019 (COVID-19) infection in February 2023, the patient’s chest CT became clear, accompanied by improved pulmonary function. Repeated HRCT of the chest in March 2024 confirmed no signs of recurrence, nor in pulmonary function tests. In this case, COVID-19 infection may have contributed to the improvement of this patient’s PAP, raising the hypothesis of an immunomodulatory effect.