Diagnostic Pitfall: Prolonged COVID-19 Presenting as Organising Pneumonia in a Rituximab-Treated Patient with Rheumatoid Arthritis.

Rituximab (RTX)-induced B-cell depletion is associated with prolonged SARS-CoV-2 infection. We describe a case of persistent COVID-19 in a patient with rheumatoid arthritis (RA) initially misdiagnosed as cryptogenic organising pneumonia (COP), highlighting the diagnostic and management challenges in RTX-treated patients. Retreatment with a second 5-day course of nirmatrelvir/ritonavir led to rapid clinical improvement and complete radiological resolution. Persistent SARS-CoV-2 infection should be considered in RTX-treated patients with non-resolving pulmonary infiltrates, particularly when corticosteroid therapy is ineffective.