Severity and prognosis of COVID-19 complicated by autoimmune pulmonary alveolar proteinosis

The prognosis of patients with coronavirus disease 2019 (COVID-19) was poor although its survival rate has been improved after the occurrence of the Omicron strain. Autoimmune pulmonary alveolar proteinosis (APAP), a lung disease caused by macrophage dysfunction induced by anti-granulocyte-macrophage colony-stimulating factor (GM-CSF)-neutralizing autoantibodies, is characterized by the deposition of proteinaceous material in the alveolar spaces. The clinical course of COVID-19 in patients with APAP remains unclear and this study aimed to clarify it.

The data of 23 patients with APAP, who were diagnosed with COVID-19 between January 2020 and May 2023 and collected through a nationwide questionnaire surveillance system, were retrospectively reviewed.

Based on the epidemiological frequency at disease onset, suspected strains of severe acute respiratory syndrome coronavirus 2 were Omicron (n = 18) and non-Omicron (n = 5). Fifteen patients were vaccinated. Six and three patients received anti-viral drugs and corticosteroids, respectively. One patient in the third trimester of pregnancy died despite treatment in the intensive care unit. Six patients were complicated by pneumonia and/or required supplemental oxygen. These patients were suspected to have non-Omicron strains (p = 0.087). Vaccination status showed a significant association with suspected Omicron strains. The radiological findings in four patients and shortness of breath improved in two of the four patients after COVID-19.

The severity and prognosis of the patients were not worse than those predicted based on the results of a previous study. The transition from a non-Omicron strain to an Omicron strain and the vaccination status may have affected these results.