Two cases of cryptogenic organizing pneumonia masquerading as tuberculosis (TB) in a TB endemic area.

Before the era of COVID-19 pandemic, organizing pneumonia (OP) is often underdiagnosed while tuberculosis (TB) is overdiagnosed especially in an endemic area. We report two patients with cryptogenic OP mimicking TB. First, a 56-year-old lady with right upper lobe air space opacity and, second, a 37-year-old lady with left upper lobe cavitary lesion. They were treated empirically for pulmonary TB as they had chronic cough with typical chest imaging findings. As there were no improvements despite anti-TB and investigations for TB were negative, they underwent image-guided biopsy which confirmed OP. Both patients received 6 months of corticosteroids therapy and made complete recovery. These cases highlight the rare presentation of OP and serves as a reminder that patients tested negative for TB, despite typical history and chest imaging findings, warrant further investigations as many diseases may mimic TB and vice versa.

Organising pneumonia manifesting as a late-phase complication of COVID-19.

Acute COVID-19 usually lasts 4 weeks from the onset of symptoms. We report two cases of COVID-19-associated organising pneumonia (OP) occurring beyond 4 weeks from the acute onset of symptoms. Both tested positive for SARS reverse transcription-PCR 2 months before presentation with a resolution of respiratory symptoms. The first case presented with residual fatigue and worsening exertional dyspnoea. Chest CT revealed an OP pattern. The second case presented with worsening cough and new-onset pleuritic chest pain with persistent radiological consolidation. A transbronchial lung biopsy confirmed OP. Both patients responded well to 12 weeks of steroid therapy. This case illustrates the rare presentation of OP as a late sequela of COVID-19 and the good response to steroid therapy.

Single dose of rituximab causing organising pneumonia in a patient with B-cell lymphoproliferative disorder.

Rituximab (RTX) is a monoclonal anti-CD20 antibody used to treat non-Hodgkin's lymphoma. RTX-organising pneumonia (RTX-OP) is a rare complication following treatment with RTX. We report a 49-year-old woman, with CD5-negative B-cell lymphoproliferative disorder who developed high-grade fever, dyspnoea and dry cough 3 days after the first dose of RTX. She responded poorly to antibiotics and antifungal therapy. High-resolution CT (HRCT) of the chest revealed bilateral patchy ground-glass opacities with arcade-like signs suggestive of OP. She was pulsed with intravenous methylprednisolone and RTX was discontinued. She was able to be weaned off the non-invasive ventilation (NIV) support and was discharged with maintenance prednisolone 1 mg/kg and tapered over 6 weeks. A repeated HRCT of the chest at 6 weeks showed a total resolution of OP. This highlights the early occurrence at day 3 of RTX-OP following the first dose of RTX and the complete resolution with steroid therapy.