• Clinical science

Diphtheria

Summary

Diphtheria is an infectious disease caused by Corynebacterium diphtheriae, which is usually transmitted via respiratory droplets. The clinical features of diphtheria are caused by a toxin produced by C. diphtheriae after it colonizes the upper respiratory tract. Patients initially present with fever, malaise, and sore throat. Within a few days, a grayish white pseudomembrane develops over the tonsils, posterior pharyngeal wall, and/or larynx. Other manifestations include cervical lymphadenopathy, soft tissue swelling of the neck, stridor, and/or difficulty breathing as a result of partial airway obstruction. Systemic absorption of the toxin can result in myocarditis, acute tubular necrosis, and/or polyneuropathy. Even before culture reports come back positive, patients should be promptly treated with penicillin and antitoxins, as untreated diphtheria is associated with a high mortality rate. Since the introduction of routine immunization against diphtheria in the 1920s, the incidence of disease has decreased dramatically in the US.

Epidemiology

  • Incidence: 0–5 cases/year
  • Most cases occur in patients 20 years of age or older.

Epidemiological data refers to the US, unless otherwise specified.

Etiology

  • Pathogen: Corynebacterium diphtheriae
    • A gram-positive, non-sporulating, club-shaped bacillus, containing metachromatic granules (AKA volutin granules).
  • Route of infection
    • Droplet transmission
    • Less commonly through direct or indirect contact with open lesions (see extra information for more details on cutaneous diphtheria)
  • Infectious period: variable

References:[1]

Pathophysiology

References:[2][3][1]

Clinical features

Respiratory diphtheria

  • Incubation period: 2–5 days
  • The patient presents initially with prodromal symptoms: fever, malaise, and sore throat
  • 4–5 days after the onset of prodromal symptoms, symptoms due to the local and systemic effects of the toxin occur

Cutaneous diphtheria

References:[2]

Diagnostics

Therapy should be started immediately upon clinical suspicion, even before diagnostic confirmation of diphtheria!

Differential diagnoses

The differential diagnoses listed here are not exhaustive.

Treatment

  • The patient should be isolated as soon as diphtheria is suspected.
  • Antibiotic therapy; : IM injections of Penicillin G or oral/IV erythromycin for 14 days
  • Immediate administration of diphtheria antitoxin: The antitoxin can only neutralize unbound toxin and should therefore be administered early in the course of the disease.
  • Airway support

Administration of the antitoxin is a critical part of treatment, as the clinical features of diphtheria are not caused by the pathogen itself but rather by the exotoxin that C. diphtheriae produces!

References:[1][4]

Prevention

Pre-exposure prophylaxis

Post-exposure prophylaxis

Post-exposure prophylaxis is indicated for close personal contacts and caretakers of a patient with diphtheria.

Diphtheria is a notifiable disease!

References:[4][5][6][7][8][9]