Abstract
Irrespective of the underlying disease, patients treated with cluster of differentiation 20 (CD20) antibodies have a higher risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) long or severe infection, and there are pitfalls in this diagnosis. We herein report two patients with COVID-19 pneumonia diagnosed by bronchoalveolar lavage fluid (BALF) during lymphoma remission. Nasopharyngeal swabs (NSs) were polymerase chain reaction (PCR)-negative for SARS-CoV-2, and the virus was only detectable in the lungs. In patients with B-cell depletion, the early performance of bronchoalveolar lavage (BAL) is important for diagnosing COVID-19 pneumonia and ruling out opportunistic infections when any evidence of suspected viral pneumonia is observed on computed tomography (CT), even if the NS specimens are PCR-negative and they have no upper respiratory symptoms. In addition, blood tests with lymphocytopenia, BALF with decreased CD4/CD8 ratio, and increased neutralizing antibody titer suggested that not only low humoral immune responses but also CD4 T-cell depletion by bendamustine were associated with virus clearance. Even if neutralizing antibodies are adequate, we must be careful of prolonged COVID-19 due to CD4 T-cell depletion and low humoral immune responses.