Vasculitis - Urticarial Vasculitis

Vasculitis is an autoimmune condition that includes a broad spectrum of disorders characterized by blood vessel inflammation and necrosis. Clinical effects depend on the vessels involved and reflect tissue ischemia caused by blood flow obstruction.

The prognosis varies with the disease form. For example, hypersensitivity vasculitis is usually benign and limited to the skin, whereas the more extensive polyarteritis nodosa can be rapidly fatal.

Except for the mucocutaneous lymph node syndrome, which affects only children, vasculitis can affect a person at any age. Vasculitis may be a primary disorder or secondary to other disorders, such as rheumatoid arthritis and systemic lupus erythematosus.

Causes

Exactly how vascular damage develops in vasculitis isn't well understood. Some think that vasculitis may follow a serious infectious disease, such as hepatitis B or bacterial endocarditis, and be related to high doses of antibiotics.

Current theory holds that vasculitis is initiated by excessive circulating antigen. which triggers the formation of soluble antigen-antibody complexes. Then, because the reticuloendothelial system can't effectively clear these complexes, they're deposited in blood vessel walls (type III hypersensitivity). Theorists think that increased vascular permeability (associated with the release of vasoactive amines by platelets and basophils) enhances this deposition. The deposited complexes activate the complement cascade. The result is chemotaxis of neutrophils, which release lysosomal enzymes. This, in turn, causes vessel damage and recrosis. These effects may precipitate thrombosis, occlusion, hemorrhage, and tissue ischemia.

An additional factor in certain types of vasculitis is the formation of autoantibodies directed at the body's own cellular and extracellular proteins, which can lead to the activation of inflammatory cells or cytotoxicity (a type II hypersensitivity reaction). Patented antibodies being studied include those directed against cytoplasmic antigens of neutrophils and monocytes (antineutrophil cytoplasmic antibodies known as CANCA or pANCA) and those directed against surface antigens of endothelial cells (antiendothelial cell antibody, or AECA). The exact role of autoantibodies remains unclear.

Another mechanism that may contribute to vascular damage is the cell-mediated (T-cell) immune response, whereby circulating antigen triggers sensitized lymphocytes to release soluble mediators. This attracts macrophages, which release intracellular enzymes, causing vascular damage. They can also transform into the epithelioid and multinucleated giant cells that typify the granulomatous vasculitides. Macrophagic phagocytosis of immune complexes enhances granuloma formation.

Atopic individuals can develop vasculitis after exposure to allergens. This type I hypersensitivity can lead to mast cell degranulation, hypereosinophilia, and inflammation, which, in turn, can lead to vasculitis.

Signs and symptoms

The signs and symptoms of vasculitis vary depending on which vessels and, as a result, which organ systems are affected. However, general signs and symptoms that most people with vasculitis experience include:

• Fever
• Fatigue
• Weight loss
• Muscle and joint pain
• Loss of appetite

Diagnostic tests

Not all vasculitis disorders can be diagnosed definitively by specific tests. The most useful general diagnostic procedure is biopsy of the affected vessel. In some disorders, arteriography may be informative.

Treatment

Appropriate treatment minimizes irreversible tissue damage associated with ischemia. In primary vasculitis, treatment may involve removal of an offending antigen or use of anti-inflammatory or immunosuppressant drugs. Antigenic drugs, food, and other offending environmental substances should be identified and eliminated, if possible.

Drug therapy in primary vasculitis typically involves daily administration of low-dose oral cyclo­phosphamide and corticosteroids. Antihypertensives and analgesics for acute pain are also given.

In rapidly fulminant vasculitis, the daily cyclophosphamide dose may be increased significantly for the first 2 to 3 days and then returned to the regular dose. In addition, the patient usually receives prednisone in daily divided doses for 7 to 10 days, with consolidation to a single morning dose by 2 to 3 weeks. When the vasculitis appears to be in remission, or when prescribed cytotoxic drugs take full effect, corticosteroid therapy is tapered to a single daily dose and then to an alternate-day schedule that may continue for 3 to 6 months.

In secondary vasculitis, treatment focuses on the underlying disorder.

Prevention

Because so little is known about what causes a particular individual to develop vasculitis, there are no known ways to prevent it.

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