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Clinical Recognition
The history should be directed toward identifying the offending agent (including
potential exposures up to 2 weeks before symptom onset), prior antigen
exposures, and reaction severity. Characteristically, symptoms develop 7 to 14
days after the primary exposure; however, among patients with prior sensitization
symptoms may develop within a few days of antigen reexposure.
Given there is significant variation in clinical manifestations and reaction
severity among patients with serum sickness, a thorough history, review of
systems, and physical examination is required to exclude systemic involvement.
Findings typically include fever, malaise, rash (urticarial, maculopapular, or
vasculitic), arthralgias, arthritis (joint swelling, warmth), lymphadenopathy,
angioedema, and nephritis (hematuria, edema, oliguria). Less common features
include abdominal pain, hepatosplenomegaly, carditis (friction rub, new murmur,
gallop), wheezing, pallor, and neurologic deficits secondary to CNS vasculitis.
Serum sickness–like reactions are generally limited to fever, pruritis, urticarial
rashes, and arthralgias. Reactions are usually self-limited and typically resolve
within 1 to 2 weeks.
Laboratory Assessment
Laboratory evaluation should be guided by reaction severity, evidence of organ
system involvement, and the degree of diagnostic uncertainty. In the majority of
cases it is appropriate to limit diagnostic testing to a urinalysis to exclude
nephritis. A list of other diagnostic tests to evaluate for complications from
immune complex–mediated disease is outlined in Table 85.2 .