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April 2007 QUIZ OF THE MONTH . . .
Sometimes there is uncertainty and even confusion about the clinical presentation and diagnosis of anaphylaxis. Which of the statements below are true or false?
1.
Skin manifestations are present in a minority of cases of anaphylaxis.
2.
Upper airways obstruction is a major cause of mortality in anaphylaxis
3.
Asthma is a very unusual manifestation in anaphylaxis
4.
The serum tryptase level is frequently increased at 4 hours after onset of an anaphylactic episode
5.
The plasma histamine level is frequently increased at 4 hours after onset of an anaphylactic episode
Discussion
In humans over 80% of anaphylactic reactions have skin manifestations, (generally flushing, urticaria). Swelling of the upper airway mucosa is also common, sometimes to a degree where fatal obstruction of the hypo pharynx and/or larynx may occur in severe cases. Less commonly, the mucosa of the G-I tract is involved, manifested as cramping abdominal pain, vomiting and occasionally diarrhea. Acute asthma is a common manifestation of anaphylaxis. Cardiac involvement, due to a direct effect and/or or reaction to hypovolemia due to marked vascular leakage, is a less common but very serious manifestation.
Histamine and tryptase are both released from mast cells in anaphylaxis. The plasma histamine levels rise very rapidly but are usually back to normal within 30-60 minutes due to rapid metabolism of histamine. Serum tryptase levels start increasing about the same time or slightly later than plasma histamine levels. However, the serum tryptase levels remain increased for at least 4 hours.
References
1. J Allergy Clin Immunol 2005;115(Suppl): S485-523
2. J Allergy Clin Immunol 2006;117:391-97
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