A 28-year-old woman is brought to the emergency department by her family due to acute left flank pain. The pain radiates to her groin and is associated with pink hematuria and urinary urgency. Past medical history is unremarkable, and the patient has never experienced similar symptoms. CT scan of the urinary system confirms the presence of a stone at the ureterovesical junction. The patient is given intravenous morphine sulfate for pain relief. Fifteen minutes later, she develops diffuse itching involving the arms, legs, and back. Which of the following is the most likely mechanism causing this patient's adverse reaction?

Question

A 28-year-old woman is brought to the emergency department by her family due to acute left flank pain.  The pain radiates to her groin and is associated with pink hematuria and urinary urgency.  Past medical history is unremarkable, and the patient has never experienced similar symptoms.  CT scan of the urinary system confirms the presence of a stone at the ureterovesical junction.  The patient is given intravenous morphine sulfate for pain relief.  Fifteen minutes later, she develops diffuse itching involving the arms, legs, and back.  Which of the following is the most likely mechanism causing this patient's adverse reaction?

Quizplus · Accepted Answer

This patient with acute pruritus following administration of morphine most likely has medication-induced IgE-independent mast cell activation. A number of medications, including opioids, radiocontrast agents, and some antibiotics (eg, vancomycin), can induce mast cell degranulation by activation of protein kinase A and PI3 kinase. This results in release of several mediators, including histamine, bradykinin, heparin, and a number of enzymes and chemotactic factors. Common symptoms include diffuse itching and pain, bronchospasm, and localized swelling (urticaria). (Choice A) IgE-mediated degranulation is typically associated with environmental exposures such as foods or vespid stings or with medications such as beta-lactam and sulfonamide antibiotics. Opioids can cause IgE-dependent degranulation (very rare), but IgE-independent reactions are more common. (Choice C) Inhibition of cyclooxygenase 1 by aspirin and nonsteroidal anti-inflammatory drugs can trigger urticaria in patients with chronic idiopathic urticaria. These medications shunt arachidonic acid metabolites toward formation of leukotrienes, which increase vascular permeability. (Choice D) Serum sickness is a type III hypersensitivity reaction caused by precipitation of circulating immune complexes. Typical symptoms include fever, pruritic rash, and arthralgias starting 7-14 days after antigen exposure. Common triggers include beta-lactam and sulfonamide antibiotics. (Choice E) Acute allergic contact dermatitis is caused by a T cell-mediated type IV (delayed) hypersensitivity reaction to an antigen on the skin surface. Gross findings include erythematous, papulovesicular, weeping lesions. Educational objective: A number of medications, including opioids, radiocontrast agents, and some antibiotics (eg, vancomycin), can trigger IgE-independent mast cell degranulation. Common symptoms include diffuse itching and pain, bronchospasm, and localized swelling (urticaria). __________ References: Pharmacological stimuli in asthma/urticaria. (http://www.ncbi.nlm.nih.gov/pubmed/17064652) Pathogenic intracellular and autoimmune mechanisms in urticaria and angioedema. (http://www.ncbi.nlm.nih.gov/pubmed/22674016) Codeine induces human mast cell chemokine and cytokine production: involvement of G-protein activation. (http://www.ncbi.nlm.nih.gov/pubmed/17441793)

A 28-Year-Old Woman Is Brought to the Emergency Department by Her