Granulomatosis with polyangiitis (GPA) is a rare autoimmune disease that causes inflammation of blood vessels, leading to damage in various organs. It primarily affects the respiratory system, kidneys, and nerves, resulting in symptoms like sinusitis, cough, and kidney dysfunction. The condition is characterized by the formation of granulomas, which are clusters of immune cells that form in response to inflammation. Diagnosis often involves blood tests for specific antibodies, imaging studies, and sometimes a biopsy of affected tissue. Treatment typically includes immunosuppressive medications to reduce inflammation and prevent organ damage.