An 8-year-old boy developed anaphylaxis after receiving his maintenance dose of
immunotherapy and proceeded to display the signs and symptoms of serum sickness. These
consisted of fever, arthralgia, arthritis, urticaria followed by a hemorrhagic palpable rash,
edema, lymphadenopathy, splenomegaly, abdominal pain, proteinuria, and neurologic
manifestations consistent with vascular compromise of the posterior cerebral circulation. A
skin biopsy specimen revealed perivascular infiltrates of lymphocytes and few …