Pulmonary manifestations associated with positive anti neutrophil cytoplasmic antibodies: The tip of the iceberg.

Background: Even though anti-neutrophil cytoplasmic antibodies (ANCA) are frequently linked to ANCA associated vasculitis (AAV), it's important to understand that other illnesses, including lung diseases, can also manifest as ANCA positivity. Finding the incriminated pathology might be difficult. Aim: To report four ANCA-associated cases with a diagnosis problem. Methods: Four patients were recruited from the allergo-pneumology department of the Fattouma Bourguiba University Hospital of Monastir, Tunisia, over two years (2020-2022). Indirect immunofluorescence technique on neutrophil cells (Euroimmun, Germany) was used for ANCA screening with a positivity limit of 1/20. ANCA typing was carried out by a line-blot technique (Euroimmun, Germany). Results: This case series reports four cases (age range: 41-67 years, sex ratio: 0.3) that presented with pulmonary manifestations associated with ANCA positivity. Two patients had perinuclear ANCA with anti-myeloperoxidase on typing, and two cases had cytoplasmic ANCA with one case of anti-leukocyte proteinase 3 on typing. Final diagnoses were pulmonary tuberculosis (case 1), systemic lupus erythematosus (case 2), bronchiolitis obliterans organizing pneumonia (case 3), and pulmonary aspergillosis with AAV (case 4). Conclusion: A panel of diagnoses may be evoked in front of positive ANCA, making the diagnosis difficult to determine and requiring multidisciplinary interactions, with imaging and histological investigations having a crucial role in guiding the final decision.