Cavitary Pneumocystis jirovecii pneumonia with dual ANCA positivity in advanced HIV infection: a case report

Pneumocystis jirovecii pneumonia (PCP) is an important opportunistic infection in advanced HIV infection and classically presents with bilateral ground-glass opacities. Cavitation is an uncommon imaging manifestation and may broaden the differential diagnosis to include mycobacterial infection, fungal infection, malignancy, and vasculitis. A 48-year-old man with previously undiagnosed advanced HIV infection presented with progressive dyspnea, weight loss, and multiple cavitary pulmonary lesions. Initial investigations for tuberculosis and respiratory viral infections were negative. Serologic testing showed dual anti-neutrophil cytoplasmic antibody (ANCA) positivity, with P-ANCA/anti-myeloperoxidase (MPO) 90 AU/mL and C-ANCA/anti-proteinase 3 (PR3) 28 U/mL, raising concern for granulomatosis with polyangiitis (GPA). The CD4 count was 55 cells/µL and the HIV-1 RNA level was 34,124 IU/mL. CT-guided lung biopsy demonstrated numerous P. jirovecii cysts without vasculitis or granulomatous inflammation, supporting a diagnosis of PCP. The patient was treated with trimethoprim-sulfamethoxazole, adjunctive corticosteroids, and antiretroviral therapy with tenofovir alafenamide, emtricitabine, and dolutegravir. Follow-up CT demonstrated marked resolution of the cavitary lesions. Cavitary PCP is an uncommon but important presentation that can mimic pulmonary vasculitis, particularly when ANCA is positive. ANCA results should be interpreted in the context of the clinical and radiologic presentation, and tissue confirmation can be particularly valuable when the findings are discordant.