Infectious Disease · Bacterial Infections
The facts most likely to be tested
Diphtheria is caused by the exotoxin-producing bacterium Corynebacterium diphtheriae, a Gram-positive club-shaped rod.
The hallmark clinical presentation is a grayish-white pseudomembrane on the tonsils, pharynx, or nasal mucosa that bleeds when scraped.
Patients often present with cervical lymphadenopathy and edema of the neck, resulting in a characteristic bull neck appearance.
The primary mechanism of action of the diphtheria toxin is the inhibition of protein synthesis via ADP-ribosylation of elongation factor-2 (EF-2).
The most critical initial step in management is the immediate administration of diphtheria antitoxin followed by erythromycin or penicillin.
Severe complications include myocarditis (manifesting as arrhythmias or heart block) and neuritis (often presenting as cranial nerve palsies).
Prevention is achieved through the DTaP or Tdap vaccine, which contains diphtheria toxoid to induce protective antitoxin antibodies.
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A 6-year-old unimmunized child is brought to the emergency department with a 3-day history of sore throat, low-grade fever, and difficulty swallowing. Physical examination reveals a thick, gray, adherent pseudomembrane covering the posterior pharynx and tonsils. The child has significant cervical lymphadenopathy and soft tissue swelling, giving the neck a bull neck appearance. The child appears toxic and has a muffled voice.
What is the most appropriate initial management for this patient?
Diphtheria antitoxin and antibiotics (erythromycin or penicillin)
The clinical presentation of a gray pseudomembrane and bull neck is pathognomonic for diphtheria; immediate administration of antitoxin is the priority to neutralize circulating toxin, as per the 5th bet.
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Etiology / Epidemiology
Caused by Corynebacterium diphtheriae; primarily affects unvaccinated individuals or those in endemic regions.
Clinical Manifestations
Presents with a gray pseudomembrane on the pharynx and bull neck appearance due to cervical lymphadenopathy.
Diagnosis
Diagnosis is clinical; confirm with culture on Loeffler's medium or tellurite agar.
Treatment
Immediate diphtheria antitoxin plus erythromycin or penicillin; do not wait for culture results.
Prognosis
Complications include myocarditis and neuritis; mortality is high if treatment is delayed.
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Epidemiology & Etiology
Caused by the aerobic, gram-positive bacillus Corynebacterium diphtheriae. Transmission occurs via respiratory droplets. Incidence is highest in unvaccinated populations and travelers to endemic areas.
Pertinent Anatomy
Infection primarily targets the pharynx, tonsils, and larynx. The toxin can spread hematogenously to affect the myocardium and peripheral nerves.
Pathophysiology
The bacteria produce an exotoxin that inhibits protein synthesis via ADP-ribosylation of elongation factor-2 (EF-2). This leads to local tissue necrosis and the formation of a thick, adherent pseudomembrane. Systemic absorption causes distant organ damage, specifically myocarditis and demyelinating polyneuropathy.
Clinical Manifestations
Patients present with sore throat, low-grade fever, and a characteristic gray, adherent pseudomembrane that bleeds if scraped. Severe cases exhibit bull neck (cervical lymphadenopathy and edema) and airway obstruction. Airway compromise is a medical emergency requiring immediate intubation.
Diagnosis
Diagnosis is primarily clinical. Definitive confirmation requires culture on Loeffler's medium or tellurite agar. PCR testing for the tox gene is used to confirm toxigenicity.
Treatment
Administer diphtheria antitoxin (equine-derived) immediately upon clinical suspicion. Follow with erythromycin or penicillin for 14 days to eradicate the carrier state. Do not delay antitoxin pending culture results.
Prognosis
The most serious complications are myocarditis (causing arrhythmias/heart block) and neuritis (cranial nerve palsies). Patients require cardiac monitoring and serial ECGs to detect early signs of conduction abnormalities.
Differential Diagnosis
Streptococcal pharyngitis: lacks the adherent gray pseudomembrane
Infectious mononucleosis: associated with posterior cervical lymphadenopathy and splenomegaly
Epiglottitis: presents with drooling and tripod positioning, not a pseudomembrane
Vincent's angina: characterized by painful ulceration and foul breath
Candidiasis: white patches are easily scraped off, unlike the diphtheria pseudomembrane