Wegener's granulomatosis, now known as granulomatosis with polyangiitis, is a rare autoimmune disease that causes inflammation of blood vessels, leading to reduced blood flow to various organs. It primarily affects the respiratory system, kidneys, and skin, resulting in symptoms such as sinusitis, cough, and kidney dysfunction. The exact cause of granulomatosis with polyangiitis is unknown, but it is believed to involve an abnormal immune response. Diagnosis typically involves blood tests, imaging studies, and sometimes a biopsy. Treatment often includes medications like corticosteroids and immunosuppressants to manage inflammation and prevent organ damage.