Diphtheria (Corynebacterium diphtheriae infection)
Diphtheria is a toxin-mediated infection by Corynebacterium diphtheriae that forms an adherent grayish pharyngeal pseudomembrane and causes myocarditis and polyneuritis; treatment is immediate equine antitoxin plus erythromycin or penicillin, and it is prevented by the DTaP/Tdap toxoid series.
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What this article covers
- Overview
Toxin-mediated upper respiratory (or cutaneous) infection: diphtheria is caused by Corynebacterium diphtheriae, a gram-positive, club-shaped rod that occurs in angular arrangements and is transmitted…
- Epidemiology
Unvaccinated and undervaccinated populations carry essentially all risk: cases occur almost exclusively in persons who never completed the primary DTaP/Tdap series or who have not received a booster…
- Risk factors
Incomplete or absent DTaP/Tdap immunization: the single dominant risk factor; disease is not expected in a fully vaccinated host.
- Pathophysiology
Local colonization of respiratory mucosa (or skin): C.
- Clinical features
Gradual-onset sore throat with low-grade fever and malaise: the classic prodrome, unlike the more abrupt onset of streptococcal pharyngitis or epiglottitis.
- Differential diagnosis
Streptococcal pharyngitis: tonsillar exudate with abrupt-onset fever and tender anterior cervical nodes, but the exudate is patchy and easily removed, not a bleeding, adherent membrane.
- Diagnosis
Diphtheria is a clinical diagnosis made at the bedside and treated on suspicion; culture on Loffler or cystine-tellurite medium with a positive Elek immunodiffusion test for toxin production provides definitive confirmation.
- Management
First, give diphtheria antitoxin (equine) intravenously as a single dose as soon as diphtheria is clinically suspected, after skin testing for horse-serum hypersensitivity with epinephrine available…
- Complications
Myocarditis with arrhythmia, heart block, or congestive heart failure: occurs in 10% to 25% of cases and is the leading cause of death, typically appearing in the second week of illness.
- Prognosis
Case fatality is highest with delayed antitoxin administration: mortality rises sharply the longer antitoxin is withheld after symptom onset, reinforcing treatment on clinical suspicion.
- Prevention
Primary childhood immunization with the DTaP series: five doses at 2, 4, 6, and 15-18 months, and 4-6 years of age for children younger than 7 years.
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