Vasculitis

Vasculitis is a general term for inflammation of blood vessel walls. 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.

Large vessel vasculitis

The large vessel vasculitides are probably mediated by cellular immunity and may have Langhans giant cells and generally have normal levels of complement system proteins and no autoantibodies. They are characterized histologically by giant cells.

Takayasu arteritis. Primarily affects the aorta and its main branches.

Giant cell (temporal) arteritis. Chronic vasculitis of both large and medium vessels, primarily affecting cranial branches of the arteries arising from the aortic arch.

Medium vessel vasculitis

The medium vessel vasculitides have similar pathology to the large vessel vasculitides.

Polyarteritis nodosa. Systemic necrotizing vasculitis and aneurysm formation affecting both medium and small arteries with sparing of the lungs and glomeruli. If only small vessels are affected, it is called microscopic polyangiitis, although it is more associated with Wegener's granulomatosis than to classic PAN.

Kawasaki disease. Usually in children, it affects large, medium, and small vessels, prominently the coronary arteries. Associated with a mucocutaneous lymph node syndrome.

Isolated CNS 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 vasculitis

There are several vasculitides that affect small vessels such as "dermal venules, mucosal arterioles, glomerular capillaries, and pulmonary alveolar capillaries."

Antineutrophil cytoplasmic antibodies associated

Some small vessel vasculitides, "Wegener's granulomatosis, microscopic polyangiitis, Churg-Strauss syndrome, and their localized forms (eg, pauci-immune necrotising and crescentic glomerulonephritis)," are associated with antineutrophil cytoplasmic antibodies (ANCA).

Vasculitides associated with antineutrophil cytoplasmic antibody (ANCA), with partial exception from microscopic polyangiitis, are associated with respiratory manifestations.

A systematic review of antineutrophil cytoplasmic antibody (ANCA) positive vasculitis identified best treatments depending on whether the goal is to induce remission or maintenance and depending on severity of the vasculitis.

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.

Immune-complex associated

These vasculitides, with partial exception from microscopic polyangiitis, are associated with dermatological manifestations.

Henoch-Schonlein purpura. Systemic vasculitis due to tissue deposition of IgA-containing immune complexes. Biopsy of lesions shows inflammation of small vessels. It is considered a form of hypersensitivity vasculitis but is distinguished by prominent deposits of IgA. 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 with palpable petechiae or purpura. Biopsy of these lesions reveal inflammation of the small vessels, termed leukocytoclastic vasculitis, which is most prominent in postcapillary venules.

Essential cryoglobulinemic vasculitis. Most often due to hepatitic C infection, immune complexes of cryoglobulins --- proteins that consists of immunoglobulins and complement and precipitate in the cold while dissolving upon rewarming --- are deposited in walls of capillaries, venules, or arterioles. Therefore, complement will be low with histology showing vessel inflammation with immune deposits.

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 and C, HIV, cytomegalovirus, Epstein-Barr virus, and Parvo B19 virus.

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.