Clinical History:

A 27-year-old man was brought to the emergency room following an episode of minor trauma in which he sustained minor bruises to his left upper arm and chest in a fall off a ladder. Approximately one hour after admission, he became suddenly short of breath, gasping for air. Despite resuscitation, he died minutes later.

Image 6.1:

The only major finding at autopsy was marked laryngeal edema, shown here. It was also noted that he had a right wrist band that said "Allergy to penicillin".

Questions:

1. What do you think happened?

The patient received penicillin by mistake. The medication record indicated that IV penicillin was started, but two minutes later was a note, "dc'd, error"

2. What immunologic mechanism is operative here?

This is a type I hypersensitivity reaction with systemic anaphylaxis. This type of reaction can occur within minutes. It is important to take a careful history of allergies. Prior sensitization has resulted in an immune response initially mediated by CD4 lymphocytes (the Th2 variety) that promote mast cell proliferation and plasma cell production of IgE. The IgE becomes bound to mast cells in places such as respiratory tract mucosa.

Another encounter with the antigen cross links the IgE and triggers mast cell degranulation with release of preformed mediators such as histamine that promotes vasodilation and edema. Release of eosinophil chemotactic factor (ECF) leads to characteristic infiltration by eosinophils in these allergic responses. The arachidonic acid pathways are stimulated in the mast cells to produce leukotrienes and prostaglandins, additional mediators of this inflammatory response.