A 12-year-old boy is brought to the emergency department due to worsening facial swelling. Thirty minutes ago, the patient began experiencing a burning sensation and swelling of the eyes. He also has had a scratchy sensation and tightness in the throat as well as crampy abdominal pain. The patient was seen at an urgent care clinic earlier today due to persistent sore throat for the past several days. He was diagnosed with acute pharyngitis and prescribed amoxicillin. The patient has no other medical conditions and no known drug allergies. Temperature is 37.2 C (99 F), blood pressure is 116/68 mm Hg, and pulse is 92/min. Physical examination shows bilateral periorbital swelling and mild conjunctival erythema. There are scattered, raised wheals on his trunk. Which of the following is most likely involved in the pathogenesis of this patient's current condition?

Question

A 12-year-old boy is brought to the emergency department due to worsening facial swelling.  Thirty minutes ago, the patient began experiencing a burning sensation and swelling of the eyes.  He also has had a scratchy sensation and tightness in the throat as well as crampy abdominal pain.  The patient was seen at an urgent care clinic earlier today due to persistent sore throat for the past several days.  He was diagnosed with acute pharyngitis and prescribed amoxicillin.  The patient has no other medical conditions and no known drug allergies.  Temperature is 37.2 C (99 F), blood pressure is 116/68 mm Hg, and pulse is 92/min.  Physical examination shows bilateral periorbital swelling and mild conjunctival erythema.  There are scattered, raised wheals on his trunk.  Which of the following is most likely involved in the pathogenesis of this patient's current condition?

Quizplus · Accepted Answer

11ec25c8_d61f_1225_bc81_4194a6279cd6_MD0003_00 This patient with sudden-onset periorbital swelling, truncal wheals, throat tightness, and crampy abdominal pain has anaphylaxis, which may be diagnosed when acute allergic symptoms are present in ≥2 organ systems (eg, skin/mucosa, gastrointestinal) after likely allergen exposure. In this patient, the probable allergen is amoxicillin. Prior administration likely initiated production of amoxicillin-specific IgE without causing an allergic response (eg, no known drug allergies). Subsequent reexposure (today) then caused mast cell activation and degranulation with release of chemical mediators (eg, histamines, prostaglandins, leukotrienes). mast cell activation This widespread release of chemical mediators results in the multisystem, broad-ranging symptoms of anaphylaxis. Increased gastrointestinal smooth muscle contraction can cause crampy abdominal pain (as in this patient), vomiting, or diarrhea. Localized vasodilation and increased capillary permeability can cause skin or mucosal manifestations, including wheals, periorbital edema, and conjunctival erythema. Often, there may be cardiovascular (eg, hypotension, tachycardia) or respiratory (eg, wheezing, stridor) involvement. Management begins with prompt administration of intramuscular epinephrine. (Choice A) Acute Epstein-Barr virus infection (ie, infectious mononucleosis) can cause pharyngitis, abdominal pain (due to splenomegaly), and a rash (if antibiotics such as amoxicillin are prescribed). However, abdominal pain is typically in the left upper quadrant and vague (rather than crampy), and the rash is typically maculopapular (not the wheals seen in this patient). In addition, fever, malaise, and cervical lymph node enlargement are commonly present. maculopapular wheals (Choice B) Group A streptococcal pharyngitis can be complicated by acute poststreptococcal glomerulonephritis (APSGN) due to immune complex formation. When severe (eg, nephritic syndrome), APSGN can cause edema from fluid retention; however, unlike in this patient, hypertension is usually present, and symptoms typically appear over days. immune complex formation (Choice C) Impaired bradykinin degradation can cause increased vascular permeability, leading to facial or visceral angioedema (eg, periorbital swelling, abdominal pain). However, this typically occurs with exposure to ACE inhibitors rather than antibiotics. In addition, bradykinin-mediated angioedema, unlike mast cell-mediated angioedema, does not cause rash (eg, wheals). (Choice E) Children with systemic vasculitis may have rash (eg, IgA vasculitis) or conjunctival injection (eg, Kawasaki disease); however, fever and additional inflammatory symptoms (eg, lymphadenopathy, joint pain) are commonly present. In addition, symptoms typically develop over days (not minutes). Educational objective: Anaphylaxis is caused by IgE-mediated mast cell degranulation in response to an allergen. It can be diagnosed when acute allergic symptoms are present in ≥2 organ systems (eg, skin/mucosa, gastrointestinal) after exposure to a likely allergen. References: The pathophysiology of anaphylaxis. (http://www.ncbi.nlm.nih.gov/pubmed/28780941) Time to revisit the definition and clinical criteria for anaphylaxis? (http://www.ncbi.nlm.nih.gov/pubmed/31719946)

A 12-Year-Old Boy Is Brought to the Emergency Department Due