A case of granulomatosis with polyangiitis mimicking lung malignancy.

Patients with granulomatosis with polyangiitis (GPA) may present with varied manifestations including pulmonary masses and nodules. We report the case of a 45-year-old man presenting with cough, haemoptysis and weight loss in the context of a 20 pack-year past smoking history. Computed tomography (CT) of the chest and positron emission tomography/CT scan demonstrated two right upper lobe masses, bilateral lung nodules and mediastinal lymphadenopathy, with increased fluorodeoxyglucose avidity. Endobronchial and CT-guided lung biopsy demonstrated granulomatous inflammation and elevated c-ANCA/PR3 confirmed the diagnosis of GPA. The patient received induction therapy with methylprednisolone and rituximab with good clinical response. Our case highlights the importance of considering a wide range of differentials in patients with lung masses/nodules, including autoimmune pathologies.