An 8-year-old boy who recently moved to the United States from Indonesia is brought to the emergency department due to fever, sore throat, and difficulty breathing. His immunization status cannot be determined. Physical examination shows extensive, coalescing, gray pharyngeal exudate and cervical adenopathy. Several days after being admitted to the hospital, he dies of myocarditis and severe heart failure. The presence of which of the following would most likely have prevented this patient's death?

Question

An 8-year-old boy who recently moved to the United States from Indonesia is brought to the emergency department due to fever, sore throat, and difficulty breathing.  His immunization status cannot be determined.  Physical examination shows extensive, coalescing, gray pharyngeal exudate and cervical adenopathy.  Several days after being admitted to the hospital, he dies of myocarditis and severe heart failure.  The presence of which of the following would most likely have prevented this patient's death?

Quizplus · Accepted Answer

11ec160b_3820_608e_9249_531243904d2d_MD0001_00 This patient with an uncertain vaccination history likely died from diphtheria, a clinical illness caused by toxigenic strains of Corynebacterium diphtheriae. The disease is rare in the developed world due to widespread vaccination with diphtheria toxoid, but outbreaks often occur in regions where vaccination efforts are insufficient (eg, Southeast Asia). Most cases are transmitted by aerosolized droplets from asymptomatic carriers or infected patients. Although the pathogen has little capacity for invasion, it generates a potent exotoxin (diphtheria toxin) that irreversibly inhibits protein synthesis through ADP-ribosylation of elongation factor-2, leading to host cell death and necrosis. Local effects of the toxin include pharyngitis and laryngotracheitis, often with an extensive, coalescing exudate (pseudomembrane). Absorption of the toxin into the bloodstream results in potentially life-threatening myocarditis and neuritis. Diphtheria can be prevented with the diphtheria-pertussis-tetanus (DPT) childhood vaccination, which generates neutralizing IgG antibodies against the binding component (B subunit) of the diphtheria exotoxin. The vaccine inhibits toxin-mediated cell damage and also reduces the competitive advantage of toxigenic strains, thereby reducing toxigenic carriage rates within the population. (Choice A) CD8 lymphocytes destroy cells infected with intracellular pathogens (eg, viruses) as well as cells damaged by cancer. They do not bind to and eliminate circulating exotoxins. (Choices B and E) IgM opsonization and complement fixation are important mechanisms for combating extracellular infections, particularly with encapsulated organisms. Although vaccination may stimulate an IgM response, long-term protection is primarily mediated by IgG antibodies. (Choice C) IgA is the primary immunoglobulin found on mucosal surfaces and in secretions. It does not have significant opsonizing or complement-activating properties. Instead, it prevents infection by inhibiting bacterial interaction with epithelial cells (eg, attachment, invasion). IgA antibodies may help prevent diphtheria colonization. However, C diphtheriae does not have a polysaccharide capsule. Educational objective: Toxigenic strains of Corynebacterium diphtheriae produce diphtheria toxin, which irreversibly inhibits host protein synthesis due to ADP-ribosylation of elongation factor-2. Local effects include pseudomembranous pharyngitis; systemic effects include potentially life-threatening myocarditis and neuritis. Immunization with diphtheria toxoid generates protective circulating IgG against the exotoxin B subunit.

An 8-Year-Old Boy Who Recently Moved to the United States