Abstract
In this article, we present an unusual case of granulomatosis with polyangiitis (GPA) in a 41-year-old man. The initial presentation of the disease was atypical, with persistent fever, cough, and fatigue, accompanied by elevated inflammatory markers in association with a large, solitary lung lesion observed at the chest X-ray. Despite the presence of an initial radiological picture suggesting pneumonia, the lack of response to antibiotics necessitated a more in-depth evaluation. The diagnosis was confirmed through a lung biopsy and serological tests positive for anti-neutrophil cytoplasmic antibodies (c-ANCA). GPA is an anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, a systemic autoimmune disease characterized by necrotizing granulomatous inflammation and pauci-immune small vessel vasculitis. This case posed diagnostic challenges due to the atypical presentation, initially mistaken for a respiratory tract infection versus cancer. However, the lack of improvement with antibiotics and persistent inflammation raised suspicions of an underlying complex condition. The diagnosis was confirmed through a lung biopsy and positive c-ANCA serological tests. The patient had reported a prior SARS-CoV-2 infection, raising questions about the possible connection between COVID-19 and GPA, as suggested by previous studies. The diagnostic workup ruled out common and rare pulmonary infections, autoimmune diseases, and neoplasms. However, the presence of positive c-ANCA antibodies was pivotal for the GPA diagnosis. Treatment involved the use of high-dose corticosteroids and rituximab to suppress the autoimmune response. Early diagnosis and timely treatment are essential for improving outcomes in patients with GPA.