From the Guidelines
The administration of denatured bacterial toxin that contains an intact receptor binding site, specifically diphtheria toxoid vaccine, at the time of her previous admission is most likely to have prevented this patient's cardiac symptoms. This patient is suffering from diphtheria myocarditis, a complication of Corynebacterium diphtheriae infection, as evidenced by the clinical presentation of pseudomembranous pharyngitis, cervical lymphadenopathy requiring intubation, and subsequent cardiac symptoms with ECG changes, including elevated cardiac troponins, diffuse T wave inversions, and prolonged PR interval 1. The patient's unvaccinated status further supports this diagnosis.
- Key features of the patient's presentation include:
- Pseudomembranous pharyngitis
- Severe cervical lymphadenopathy
- Cardiac symptoms with ECG changes
- Elevated cardiac troponins
- Diphtheria toxin causes myocardial damage by inhibiting protein synthesis in cardiac cells, leading to complications like myocarditis 1.
- Administration of diphtheria toxoid vaccine, a denatured form of the toxin that retains its antigenic properties, would have stimulated antibody production against the toxin, preventing the cardiac complications 1.
- The toxoid vaccine is part of the routine childhood immunization schedule as DTaP (diphtheria, tetanus, acellular pertussis), and prevention through vaccination is most effective at preventing complications like myocarditis 1.
From the FDA Drug Label
Diphtheria is an acute toxin-mediated disease caused by toxigenic strains of C. diphtheriae. Protection against disease is due to the development of neutralizing antibodies to diphtheria toxin. A serum diphtheria antitoxin level of 0.01 International Units (IU)/mL is the lowest level giving some degree of protection, and levels of at least 0. 1 IU/mL are generally regarded as protective.
The administration of diphtheria antitoxin (choice A, denatured bacterial toxin that contains an intact receptor binding site) at the time of her previous admission is most likely to have prevented this patient's cardiac symptoms, as it would have provided protection against diphtheria toxin, which can cause cardiac complications 2.
From the Research
Cardiac Symptoms Prevention
The patient's cardiac symptoms, including elevated cardiac troponins, diffuse T wave inversions, and prolonged PR interval, are likely due to myocarditis caused by diphtheria toxin.
- The administration of diphtheria antitoxin at the time of her previous admission is most likely to have prevented this patient's cardiac symptoms 3, 4, 5.
- Diphtheria antitoxin is an immunoglobulin preparation that neutralizes circulating diphtheria toxin, which is responsible for the systemic effects of the disease, including myocarditis 4, 5.
- The use of diphtheria antitoxin has been shown to be effective in treating diphtheria and preventing its complications, including cardiac symptoms 3, 4, 5.
- Alternative treatments, such as human recombinant antibodies or IgY polyclonal antibody, are being developed, but diphtheria antitoxin remains the most widely used and effective treatment for diphtheria 6, 7.
Treatment Options
The options for preventing the patient's cardiac symptoms are:
- A. Denatured bacterial toxin that contains an intact receptor binding site: This is not a treatment for diphtheria, but rather a description of the diphtheria toxin itself.
- B. Electrolyte that reduces cardiomyocyte excitability: This is not a specific treatment for diphtheria or its cardiac complications.
- C. Antibiotic that binds to penicillin-binding protein 3: Antibiotics are used to treat the bacterial infection, but they do not neutralize the diphtheria toxin.
- D. Salicylate that inhibits prostaglandin synthesis: This is not a treatment for diphtheria or its cardiac complications.
- E. Immunoglobulin that targets circulating proteins: This is a description of the diphtheria antitoxin, which is the correct answer.