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A 52-year-old woman comes to the emergency department with pain and redness affecting her left leg. The patient's symptoms began 2 days ago and have progressed to the point where she cannot walk without experiencing severe pain. Physical examination shows a large, erythematous area with indistinct margins over her left leg. The area feels hot and indurated and is exquisitely tender. She is admitted to the hospital for severe left leg cellulitis and is started on intravenous cefazolin. Several minutes after the infusion is started, she experiences shortness of breath, diffuse itching, and dizziness. Her blood pressure is 64/38 mm Hg and heart rate is 130/min. On examination, there is a diffuse erythematous skin rash and bilateral wheezing is heard on lung auscultation.
Item 1 of 2
Which of the following is most likely to be elevated in this patient's serum as a result of her medication reaction?
Anaphylaxis | |
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This patient is experiencing an anaphylactic reaction to the cephalosporin cefazolin. Anaphylaxis is a systemic type I hypersensitivity reaction characterized by increased vascular permeability and multisystem edema, leading to massive shifting of intravascular fluid to the extravascular compartment. Symptoms often begin within seconds to minutes after intravascular exposure to an inciting factor (eg, insect stings, intravenous medications) but can take up to 2 hours to develop with orally ingested antigens.
Anaphylaxis results from widespread mast cell and basophil degranulation and resultant histamine and tryptase release. Tryptase is an enzyme that is relatively specific to mast cells, and elevated serum levels of tryptase are often used to support a clinical diagnosis of anaphylaxis after the patient has been stabilized.
(Choice A) Alkaline phosphatase is present in all cells of the body, but the highest levels are found in the liver, bones, and placenta.
(Choice B) Calcitonin is produced by the C cells of the thyroid gland and can be useful as a tumor marker for medullary thyroid carcinoma.
(Choices C and D) Collagenases breakdown collagen. Myeloperoxidase catalyzes formation of hypochlorous acid (ie, bleach) during the oxidative burst in the immune response to infection. These enzymes are found predominantly in neutrophils and are not significantly elevated during an acute allergic reaction.
Educational objective:
Anaphylaxis is the result of widespread mast cell and basophil degranulation and the release of preformed inflammatory mediators, including histamine and tryptase. Tryptase is relatively specific to mast cells and can be used as a marker for mast cell activation.