Immune Complex Disease (Serum Sickness)

Artikel terkait : Immune Complex Disease (Serum Sickness)

Immune Complex Disease (Serum Sickness) Essentials of Diagnosis Fever, pruritus, and arthropathy. Reaction is delayed in onset, usually 7–10 days, when specific IgG antibodies are generated against the allergen. Immune complexes found circulating in serum or deposited in affected tissues. General Considerations Serum sickness reactions occur when immune complexes are formed by the binding of antigens (eg, drugs, heterologous serum) to antibodies. Deposition of these complexes in tissues or in vascular endothelium can produce immune complex-mediated tissue injury by activation of complement, generation of anaphylatoxins, chemoattraction of polymorphonuclear leukocytes, and tissue injury. The commonly affected organs include skin (urticaria, vasculitis), joints (arthritis), and kidney (nephritis). Clinical Findings Symptoms and Signs Constitutional symptoms, such as drug fever, are common. Laboratory Findings The specific IgG antibody may be present in sufficient quantity in serum to be detected by the precipitin-in-gel method. Detection of these precipitating antibodies by gel diffusion can be useful in the diagnosis of allergic bronchopulmonary aspergillosis or hypersensitivity pneumonitis. Enzyme-linked immunosorbent assay (ELISA) will detect antibodies present in lesser amounts. Circulating antigen-nonspecific immune complexes can be detected in a variety of malignancies and in autoimmune, hypersensitivity, and infectious diseases. Immunohistochemical techniques can identify immune complexes or complement fragments deposited in tissue biopsy specimens. Depressed serum levels of C3, C4, or CH50 may be sought as nonspecific evidence of immune complex disease with consumption of soluble factors. The erythrocyte sedimentation rate is increased, and other nonspecific laboratory findings may include elevated hepatic aminotransferases or reduced complement levels. Circulating immune complexes may be found, but current assays are limited in sensitivity. Evidence of nephritis may be found by observing red cell casts at urinalysis. Treatment This disease is self-limited, so treatment is usually conservative. Aspirin will relieve the arthralgias. Antihistamines and topical corticosteroids will control the dermatitis. Corticosteroid therapy may be necessary for serious reactions—especially glomerulonephritis, neuropathy, and other manifestations of vasculitis.

Pseudoallergic Reactions These reactions resemble immediate hypersensitivity reactions but are not mediated by allergen-IgE interaction. Instead, direct mast cell activation occurs. Examples of pseudoallergic or "anaphylactoid" reactions include the now rare "red man syndrome" from rapid infusion of vancomycin, direct mast cell activation by opioids, and radiocontrast reactions. In contrast to IgE-mediated reactions, these can often be prevented by prophylactic medical regimens. Radiocontrast Media Reactions Reactions to radiocontrast media do not appear to be mediated by IgE antibodies, yet clinically they are similar to anaphylaxis. If a patient has had an anaphylactoid reaction to conventional radiocontrast media, the risk for a second reaction upon reexposure may be as high as 30%. Patients with asthma or those being treated with B-adrenergic blocking medications may be at increased risk. The management of patients at risk for radiocontrast medium reactions includes use of the low-osmolality contrast preparations and prophylactic administration of prednisone (50 mg orally every 6 hours beginning 18 hours before the procedure) and diphenhydramine (25–50 mg intramuscularly 60 minutes before the procedure). The use of the lower-osmolality radiocontrast media in combination with the pretreatment regimen decreases the incidence of reactions to less than 1%. Immunodeficiency Disorders: Introduction The primary immunologic deficiency diseases include congenital and acquired disorders of humoral immunity (B cell function) or cell-mediated immunity (T cell function). Most of these diseases are rare, and since they are genetically determined, are seen primarily in children. Several immunodeficiency disorders affect adults, and are discussed below. Selective Immunoglobulin A Deficiency Selective IgA deficiency is the most common primary immunodeficiency disorder and is characterized by the absence of serum IgA with normal levels of IgG and IgM; its prevalence is about 1:500 individuals. Most persons are asymptomatic because of compensatory increases in secreted IgG and IgM. Some affected patients have frequent and recurrent infections such as sinusitis, otitis, and bronchitis. Some cases of IgA deficiency may spontaneously remit. When IgG2 subclass deficiency occurs in combination with IgA deficiency, affected patients are more susceptible to encapsulated bacteria and the degree of immune impairment can be more severe. Patients with a combined IgA and IgG subclass deficiency should be assessed for functional antibody responses to glycoprotein antigen immunization. Atopic disease and autoimmune disorders can be associated with IgA deficiency. Occasionally, a sprue-like syndrome with steatorrhea has been associated with an isolated IgA deficit. Treatment with commercial immune globulin is ineffective, since IgA and IgM are present only in trace quantities in these preparations. Frequent infusions of plasma (containing IgA) or unwashed blood transfusions are hazardous, since anti-IgA antibodies may develop, resulting in systemic anaphylaxis or serum sickness. Recources: Current Medical Diagnosis & Treatment 2008 Stephen J. McPhee, Maxine A. Papadakis, and Lawrence M. Tierney, Jr., Eds. Ralph Gonzales, Roni Zeiger, Online Eds.