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Histamine- and leukotriene-induced subscutaneous smooth muscle contraction
9%
3/33
Type IV hypersensitivity reaction
30%
10/33
Histamine-mediated vasodilation with increased vascular permeability resulting in dermal fluid accumulation
55%
18/33
Acquired anti-desmoglein antibodies disrupt keratinocyte adherence, leading to epidermal bullae
0%
0/33
Latent antibodies attack basement membrane, resulting in the formation of subepidermal blisters.
3%
1/33
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This patient is suffering from an anaphylactic reaction. Urticaria is due to histamine and leukotriene (mast cell-mediators) induction of vasodilation and vascular permeability, leading to fluid accumulation in the superficial dermis. Anaphylaxis to penicillin or one of its derivatives presents with pruritis, urticaria, shortness of breath, wheezing, and hypotension in the setting of a recent new medication. Systemic anaphylaxis is a type I hypersensitivity reaction. Release of mast cell mediators such as histamine leads to increased vascular permeability and smooth muscle contraction in the respiratory and gastrointestinal tracts (bronchospasm and nausea/vomiting/diarrhea). In this case, initial exposure to the allergen with the first prior ear infection treatment sensitized the patient to the drug; upon re-exposure to amoxicillin, an anaphylactic reaction ensues. Arnold et al. discuss the recognition and management of anaphylaxis. Anaphylaxis is most commonly triggered by food, insect stings, or medications and presents in most patients with predominantly respiratory and dermatologic symptoms/signs. Epinephrine is most effective at the onset of anaphylaxis, before respiratory failure and/or cardiovascular compromise takes place. Other helpful treatments include histamine H1 receptor antagonists and corticosteroids. Kuruvilla et al. review anaphylactic drug reactions and causative agents. Overall, beta-lactam antibiotics are the most common cause of drug-induced anaphylaxis. Classes of medications associated with anaphylaxis include antibiotics, radiocontrast agents, and NSAIDs. Skin-testing is often helpful in determining the risk of anaphylaxis. Figure A shows hives in a patient suffering from anaphylaxis to a penicillin-derivative. Illustration A summarizes the different types and corresponding manifestations of penicillin reactions. Incorrect Answers: Answer 1: Histamine and leukotriene do induce smooth muscle contraction, but this manifests in the respiratory tract with bronchospasm and in the GI tract with nausea/vomiting/diarrhea; smooth muscle does not play a role in the development of urticarial skin lesions in anaphylaxis. Answer 2: Anaphylaxis is a type I hypersensitivity reaction; contact dermatitis is a type IV hypersensitivity reaction. Answer 4: Acquired anti-desmoglein antibodies disrupting keratinocyte adherence, leading to epidermal bullae describes the pathophysiology of pemphigus vulgaris. Answer 5: Bullous pemphigoid is characterized by latent antibodies attacking the basement membrane zone, resulting in the formation of subepidermal blisters.
5.0
(3)
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