Serum sickness is a relatively rare condition
in humans, related to the decrease in usage of foreign serum proteins
in treatment of human disease, such as for treatment of snake
or spider bite. Similar reactions are seen in relation to streptokinase,
occasionally with bee stings but most commonly after a course
of medication such as sulphur drugs, Penicillin or Cepholosporins.
The pathogenesis appears to be that the foreign
serum, venom or medication in question is recognized as foreign
by the immune system This is followed by the generation of IgG
or IgM antibodies, typically 4 - 10 days after initial exposure.
As these antibodies bind and interact with the excess foreign
"antigen" (foreign serum or medication) circulating
immune complexes consisting of antibody and "foreign antigen"
are formed and deposited in various organs such as the kidney,
skin or joints. Clinical manifestations such as fever, urticarial
vasculitis, lymphadenopathy or joint swelling and pain can result.
Symptoms generally resolve over a period of days or weeks.
Whilst serum sickness if clearly an immunological reaction, it is not allergic in the strict definition of the word, since IgE antibodies are generally not produced. The implication is that neither RAST testing nor skin testing (which measure IgE) are useful in the confirmation of sensitivity. Diagnosis relies on the recognition of serum sickness as a syndrome, as well as the context in which it occurred. Confirmatory tests such as immune complexes have limited availability in Australia, although measurements of C3 & total haemolytic complement with or without biopsy of suspicious skin lesions are sometimes useful measures. Serum sickness is usually self limiting and resolves over 2-3 weeks. Treatment with antihistamines, non-steroidal agents or even oral corticosteroids is sometimes required to hasten recovery and control distressing symptoms.
