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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. |
