Vasculitis

Vasculitis is a general term for inflammation of blood vessel walls, resulting in ischemia of distal tissues. Most vasculitides are autoimmune diseases and the treatment involves immunosuppression or immunomodulation.

Classification

Vasculitides can be classified by the size of the blood vessel that they predominantly affect. The following is based on Table 1 and Table 2 of Jennette.

Classification of vasculitis

		Examples
Large vessel Associated with Type IV, cellular (delayed), hypersensitivity. May have Langhans giant cells on biopsy, normal levels of complement system proteins, and no autoantibodies.		Takayasu arteritis. Primarily affects the aorta and its main branches. Patients are usually less than 50 years old. May be associated with anti-endothelial cell antibody. Giant cell (temporal) arteritis. Chronic vasculitis of both large and medium vessels, primarily affecting cranial branches of the arteries arising from the aortic arch. Patients are usually over 50 years old.
Medium vessel		Polyarteritis nodosa. Systemic necrotizing vasculitis and aneurysm formation with sparing of the lungs and glomeruli. Blood tests for autoimmunity are usually normal; however, tests for inflammation (such as the erythrocyte sedimentation rate) may be abnormal. Kawasaki disease. Affects vessels of all sizes especially the coronary arteries. Usually in children and is associated with a mucocutaneous lymph node syndrome. Thromboangiitis obliterans (Buerger's disease). Blood tests for inflammation (including the erythrocyte sedimentation rate) and autoimmunity are usually normal. Isolated central nervous system vasculitis. Affects medium and small arteries over a diffuse CNS area, without symptomatic extracranial vessel involvement. Patients have CNS symptoms as well as cerebral vasculitis by angiography and leptomeningeal biopsy.
Small vessel Associated with Type III, immediate hypersensitivity. Affect the "dermal venules, mucosal arterioles, glomerular capillaries, and pulmonary alveolar capillaries."	ANCA Antineutrophil cytoplasmic antibodies (ANCA) are associated with some small vessel vasculitides including their localized forms such as pauci-immune necrotising and crescentic glomerulonephritis. With partial exception from microscopic polyangiitis, these vasculitides are associated with respiratory manifestations.	Wegener's granulomatosis. Systemic vasculitis of medium and small arteries, including venules and arterioles. Produces granulomatous inflammation of the respiratory tracts and necrotizing, pauci-immune glomerulonephritis. Most common cause of saddle nose deformity in USA (nose flattened due to destruction of nasal septum by granulomatous inflammation). Almost all patients with Wegener's have c-ANCA, but not vice versa. Churg-Strauss arteritis. Affects medium and small vessels with vascular and extravascular granulomatosis. Classically involves arteries of lungs and skin, but may be generalized. The triad asthma, eczema and renal abnormalities (e.g., red blood cell casts in urine) should raise suspicion, calling for an eosinophil count. Eosinophilia, with this clinical presentation, is grounds for a preliminary diagnosis, but immunologic confirmation is needed. Microscopic polyarteritis/polyangiitis. Affects capillaries, venules, or arterioles. Thought to be part of a group that includes Wegener's since both are associated with ANCA and similar extrapulmonary manifestations. Patients do not usually have symptomatic or histologic respiratory involvement.	Treatment depends on whether the goal is to induce remission or maintenance and depends on severity of the vasculitis.
	Immune complex These vasculitides are associated with immune complexes. With partial exception from microscopic polyangiitis, are associated with dermatological manifestations. With the exception of Henoch-Schonlein purpura, serum levels of complement system proteins may be low i nthese vasculitides.	Henoch-Schonlein purpura (HSP). Systemic vasculitis due to tissue deposition of IgA-containing immune complexes. This is the most common vasculitis in children. Hypersensitivity vasculitis. Usually due to a hypersensitivity reaction to a known drug. There is presence of skin vaculitis termed leukocytoclastic vasculitis with palpable petechiae or purpura. Most prominent in postcapillary venules. Essential cryoglobulinemic vasculitis. Most often due to hepatitis C infection, immune complexes of cryoglobulins. Vasculitis secondary to connective tissue disorders. Usually secondary to systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), relapsing polychondritis, Behcet's Syndrome, and other connective tissue disorders. Vasculitis secondary to viral infection. Usually due to hepatitis B virus and hepatitis C virus, Human Immunodeficiency Virus Type 1 (HIV), cytomegalovirus, Epstein Barr virus, and Parvovirus B19.

Treatment

In general, treatment involves immunosuppression, usually starting with corticosteroids but often using cytotoxic agents such as cyclophosphamide or methotrexate as well. Plasmapheresis may be useful. Immunologic therapies are evolving.