Diphtheria is a vaccine-preventable, toxin-mediated bacterial disease caused by Corynebacterium diphtheriae.
Outbreaks still occur across the globe in populations with low vaccine coverage. Sporadic cases occur in settings where vaccine coverage is high, mainly focused among vulnerable individuals who have arrived from places of higher risk.
Respiratory diphtheria is the main clinical presentation. Local, toxin-mediated inflammation can cause life-threatening upper airway obstruction. Systemic dissemination of toxin can cause delayed mortality from cardiac and neurologic damage.
Cutaneous diphtheria is another common presentation; it is usually less severe.
Early intervention by administering antitoxin is key to preventing severe manifestations of the disease. Prompt administration of antitoxin is necessary to deactivate free toxin in serum before it enters cells.
Antibiotic treatment is required to eliminate the bacteria and prevent further transmission. Protective immunity does not always develop after recovery, so toxoid vaccination of patients, contacts, and the general population is important for diphtheria prevention and control.
To minimize transmission, patients with respiratory diphtheria require respiratory and contact precautions (including isolation, facemasks, gloves, and gowns), and those with cutaneous diphtheria require contact isolation, ideally until cultures taken after completion of therapy are negative.
Most disease transmission is attributable to symptomatic cases, but asymptomatic carriers also play a role.
Respiratory diphtheria is an upper respiratory tract illness caused by exotoxin-producing strains of Corynebacterium diphtheriae. Rarely, it may also be caused by other corynebacteria that produce diphtheria toxin, such as Corynebacterium ulcerans or Corynebacterium pseudotuberculosis. It is characterized by sore throat, fever, and an adherent pseudomembrane that can cover tonsils and the mucosa of the pharynx, larynx, and nose. Occasionally, the mucosa of the eyes, ears, or genitals may also be affected. Enlarged anterior cervical lymph nodes and edema of the surrounding soft tissue can cause a characteristic "bull-neck" appearance. The toxin causes tissue necrosis and formation of the pseudomembrane. It also causes the major late complications of myocarditis and neuritis.
Cutaneous diphtheria may be caused by toxigenic or nontoxigenic strains of C diphtheriae and is usually a milder disease, causing cutaneous sores or shallow ulcers. Toxic complications are rare in cutaneous disease.
History and exam
Key diagnostic factors
- typical age group (<15 years or >25 years)
- exposure to infected individual
- travel from epidemic or endemic regions
- unvaccinated/incompletely vaccinated individuals
- sore throat
- dysphagia or dysphonia
- croupy cough
- pseudomembrane formation
- swelling of the neck
- skin lesions
- respiratory compromise
Other diagnostic factors
- unvaccinated individuals
- inadequately vaccinated individuals
- exposure to an infected individual
- travel from endemic areas
- skin breakdown
- poor hygiene, overcrowding, and poverty
1st investigations to order
- bacteriologic culture and microscopy
Investigations to consider
- Elek test for toxigenicity
- polymerase chain reaction (PCR)
- diphtheria antibodies
close contacts of respiratory and cutaneous cases
- Streptococcus pyogenes pharyngitis
- Acute epiglottitis
- Infectious mononucleosis
- Adult immunization schedule: recommendations for ages 19 years or older, United States, 2023
- Child and adolescent immunization schedule: recommendations for ages 18 years or younger, United States, 2023
DTaP vaccine (diphtheria, tetanus, polio, and pertussis)More Patient leaflets
- Log in or subscribe to access all of BMJ Best Practice
Use of this content is subject to our disclaimer