A rare disorder which causes inflammation of blood vessels (vasculitis) in the upper respiratory tract (nose, sinuses, ears), lungs, and kidneys. Many other areas of the body may also be affected, with arthritis (joint inflammation) occurring in almost half of all cases. The eyes and skin may also be affected.

The cause is unknown, but Granulomatosis with Polyangitis is thought to be an autoimmune disorder and is often classified as one of the rheumatic diseases. Destructive lesions develop in the upper and lower respiratory tract and the kidney. In the kidney, these lesions cause glomerulonephritis that may result in hematuria (blood in the urine) and kidney failure. It occurs most often between the ages of 30 to 50, and men are affected twice as often as women. It is rare in children, but has been seen in infants as young as 3 months old.

The kidney disease can progress rapidly, with kidney failure occurring within months of the intial diagnosis. If untreated, kidney failure and death occur in more than 90% of all patients with Granulomatosis with Polyangitis.