COVID-19 and severe pulmonary alveolar proteinosis (PAP): A case report

Pulmonary alveolar proteinosis (PAP) is a rare lung disease that mainly presents with dyspnea. PAP diagnosis can be easily missed in the background of a coronavirus disease 2019 (COVID-19) infection, due to the similarity of their presentation and radiological findings. We present a case report of a post-COVID-19 patient, who later developed severe PAP.

A 55-year-old male patient presented to the emergency department with progressive exertional dyspnea and hypoxia following a COVID-19 infection. Chest X-ray showed severe bilateral infiltrates. Patient received multiple courses of broad-spectrum antibiotics and prolonged course of corticosteroids without improvement. "Crazy paving" appearance in a follow up chest computed tomography raised the suspicion of PAP of what was initially thought to be a post-COVID-19 syndrome presentation. A diagnostic segmental bronchioalveolar lavage with a lung biopsy revealed a proteinaceous material filling the alveoli, with a positive periodic acid-Schiff (PAS) stain. Due to severe hypoxia, therapeutic segmental followed by whole lung lavage was performed with significant improvement.

Diagnosing PAP is challenging due to the rarity of the disease. An accurate diagnosis of PAP requires a combination of medical history, imaging, and bronchoalveolar lavage staining positive for PAS. Decision whether to treat with a segmental or whole lung lavage is individualized to each patient. Further studies are needed to confirm whether COVID-19 or long-term use of steroids might be contributing to PAP.