In Goodpasture's syndrome, antibodies collect in both the kidney glomerulus and the tiny air sacs (alveoli) in the lungs, causing both glomerulonephritis and bleeding in the lungs.

The exact cause is unknown. It is an autoimmune disorder, which means that immune cells attack the body's own organs, causing inflammation. Sometimes the disorder is triggered by a viral respiratory infection or by inhalation of hydrocarbon solvents. In such cases, the immune system may attack organs or tissues because it mistakes them for these viruses or foreign chemicals.

There is an inherited predisposition for Goodpasture's syndrome and researchers believe that the gene or genes involved affect the way the immune system reacts to certain invaders, increasing the likelihood mistaken identity in the lungs and kidneys.

Antibody deposits in the lungs cause bleeding within the lung tissues, resulting in the bloody sputum, which may be one of the first symptoms of the disorder. Other early symptoms include protein and blood in the urine. The condition progresses rapidly to kidney failure. Iron deficiency anemia may be present, as well as anemia associated with renal failure, and may be worse than expected considering the amount of kidney damage.