Polyarteritis nodosa is a serious autoimmune related blood vessel disease. The small and medium-sized arteries become swollen and damaged. Arteries are the blood vessels that carry oxygen-rich blood to organs and tissues. The cause of polyarteritis nodosa is unknown. The condition occurs when certain immune cells attack the affected arteries. More adults than children get this disease. The tissues that are fed by the affected arteries do not get the oxygen and nourishment they need. Damage occurs as a result. People with active hepatitis B or hepatitis C may develop this disease. Symptoms are caused by damage to affected organs. The skin, joints, muscle, gastrointestinal tract, heart, kidneys, and nervous system are often affected. Symptoms include: abdominal pain, decreased appetite, fatigue, fever, joint aches, muscle aches, unintentional weight loss, and weakness. If nerves are affected, you may have numbness, pain, burning, and weakness. Damage to the nervous system may cause strokes or seizures. Current treatments with steroids and other drugs that suppress the immune system can improve symptoms and the chance of long-term survival. The most serious complications usually involve the kidneys and gastrointestinal tract.