WG and MPA are two autoimmune disorders that cause systemic vasculitis. WG commonly affects the upper respiratory tract, the lungs, and the kidneys. MPA is marked by kidney inflammation, weight loss, skin lesions, nerve damage, and fever. Many patients with WG or MPA show no visible symptoms of active disease; it is known that underlying subclinical disease activity leads to long-term damage in these patients. Also, because it is difficult to monitor WG and MPA disease activity, it is difficult for clinicians to know when and how to treat these patients. This study will use new scientific methods to identify new biomarkers that can be used to monitor disease activity in WG and MPA patients. These biomarkers may be used to help direct clinical care for WG and MPA patients and assist in future drug development.

This study will last 5 years. Study visits will occur monthly for the first year, then every 3 months thereafter for the remainder of the study. Blood and urine collection will occur at every visit. A physical exam and medical and medication history will occur every 3 months; also, participants will be asked to complete several questionnaires to assess disease activity, health status, and tobacco, alcohol, and drug use. Participants may have additional study visits if a disease flare or disease-related complications occur during the study.

Individuals with Wegener's granulomatosis and microscopic polyangiitis. Enrollment will be sequential and participants will have disease in various stages and of different duration.

Inclusion Criteria:

• Diagnosis of WG or MPA. Widely accepted diagnostic criteria, as opposed to classification criteria or definitions, have not been developed for WG and MPA.

• For diagnosis of WG, meets at least 2 of the following 5 modified American College of Rheumatology (ACR) criteria:

  1. Nasal or oral inflammation with oral ulcers or nasal discharge with pus or blood
  2. Abnormal chest radiograph with nodules, fixed infiltrates, or cavities
  3. Urinary sediment with microhematuria or red cell casts
  4. Granulomatous inflammation within the wall of an artery or in the perivascular area on biopsy
  5. Antineutrophil cytoplasmic antibody (ANCA) positive by enzyme immunoassay for either PR3- or MPO-ANCA

• For diagnosis of MPA, meets the Chapel Hill Consensus Conference Definition for MPA:

  1. Necrotizing vasculitis, with few or no immune deposits, that affects small vessels (i.e., capillaries, venules, arterioles)
  2. Necrotizing arteritis involving small- and medium-sized arteries may be present
  3. Necrotizing glomerulonephritis is very common
  4. Pulmonary capillaritis often occurs
• Parent or guardian willing to provide informed consent, if applicable

Exclusion Criteria:

• Simultaneous diagnoses of both WG and MPA
• Churg-Strauss syndrome
• Takayasu's arteritis
• Giant cell arteritis
• Polyarteritis nodosa
• Cogan's syndrome
• Behcet's disease
• Sarcoidosis
• Kawasaki's disease
• Tuberculosis or any atypical mycobacterial infections
• Deep fungal infections
• Lymphoma, lymphomatoid granulomatosis, or any other type of cancer that mimics anti-neutrophil cytoplasmic antibody-associated vasculitis (AAVs)
• Cryoglobulinemic vasculitis
• Systemic lupus erythematosus
• Rheumatoid arthritis
• Mixed connective tissue disease or any overlapping autoimmune syndrome