Patient description: A 57-year-old man was admitted to the clinic because of weight loss and persistent dry cough 4 months ago. Chest computed topography showed bilateral multiple infiltrates in the upper lobes and thickened bronchial walls. There is a documented positive serum MPO-ANCA in his medical record. Transbronchial biopsy revealed necrotic granulomas with multinucleated giant cells and the Wegener's granulomatosis was diagnosed for him. He is treating with corticosteroid and cyclophosphamides since 4 months ago. His Birmingham Vasculitis Activity Score (BVAS) is above 4 since the beginning of his disease. His last physical exam and lab study was performed yesterday and showed the results bellow: A wellbeing, well-nourished man, non-icteric, cooperative and alert Weight: 73 kg Height: 177 BP: 120/80 HR: 90/min RR: 22/min Hgb: 13 g/dl WBC: 8000 /mm3 (Neutrophil: 2700/mm3) Plt: 300000 /ml AST: 40 U/L ALT: 56 U/L Alk P: 147 U/L Bill total: 1.2 mg/dl ESR: 120 mm/hr MPO-ANCA: 153 EU

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Wegener's Granulomatosis Microscopic Polyangiitis Churg Strauss Syndrome Polyarteritis Nodosa Giant Cell Arteritis Takayasu Arteritis for Classification 1. Adult patients aged >18 years. There is no upper age limit. 2. Ability to give informed consent. If the patient is unable to give informed consent as a result of death or physical incapacity, then informed assent from next of kin. 3. Presumed diagnosis of a primary systemic vasculitis  for classification 1. Patients < 18 years of age. 2. Inability to provide informed consent. 3. Hepatitis B or C 4. Co-morbidities that explain the clinical symptoms and signs on which the diagnosis of vasculitis is made. E.g. infection, tumour, other inflammatory condition, etc. for diagnostic 1. Adult patients aged >18 years. There is no upper age limit. 2. Ability to give informed consent. If the patient is unable to give informed consent as a result of death or physical incapacity, then informed assent from next of kin. 3. Suspected diagnosis of a primary systemic vasculitis for controls group for diagnostic 1. Adult patients aged >18 years. There is no upper age limit. 2. Ability to give informed consent. If the patient is unable to give informed consent as a result of death or physical incapacity, then informed assent from next of kin. 3. Patients presenting to secondary care with one of the following clinical presentations: I.Multi-system disease. Presentation of disease with at least 2 organs involved. II.Pulmonary-renal syndrome. Defined as haemoptysis / pulmonary haemorrhage with acute renal impairment. III.Acute renal failure IV.Acute respiratory distress. V.Chronic upper airways symptoms and signs. VI.Inflammatory polyarthritis. VII.Fever of unknown origin. VIII.Acute or chronic abdominal pain IX.Hypertension. X.Referred to secondary care with suspicion of vasculitis but confirmed not to have vasculitis. XII.New onset headache. XIII.Jaw or tongue pain. XIV.Sudden visual loss. XV.Limb claudication. XVI.Aortic aneurysm >5cm for diagnostic 1. Patients under the age of 18 2. Patient or next of kin unable or unwilling to provide informed consent or assent