Serum sickness is an immune-complex mediated reaction which may occur in patients after treatment with antithymocyte globulin (ATG) i.e. ATGAM® or Thymoglobuline®. Serum sickness presents with significant morbidity but is usually self-limiting or resolves rapidly with corticosteroid treatment.
During serum sickness, the immune system falsely identifies a protein in antiserum as a potentially harmful substance. The result is a faulty immune system response that attacks the antiserum. Immune system elements and antiserum combine to form immune complexes, which cause inflammation and other symptoms.
Symptoms usually develop 7 to 21 days after the start of treatment with ATG, however some patients may develop symptoms in 1 to 3 days if they have previously been exposed to ATG.