Inflammation of large and medium-sized arteries, leading to tissue alteration. The process can occur anywhere in the body and is caused by deficiencies of the autoimmune system. Symptoms depend on the site of the disorder. General symptoms include fever, fatigue and weight loss; the affected blood vessel walls can rupture, causing haemorrhage; also metabolic changes may cause blood-clot formation, which can block a blood vessel. Other possible symptoms are headache, muscular pain, pain in the joints and kidney abnormalities. The most specific symptom is the occurrence of small nodules in the blood vessels, which can sometimes be felt under the skin. The course of the illness varies from scarcely noticeable to severe, depending on the organ affected. Severe forms are treated with corticosteroids.