Diphtheria is endemic in many areas of the world and still occurs sporadically in the US.
Early intervention by administering antitoxin is key to preventing systemic manifestations of the disease, which can include respiratory and neurological symptoms, cardiovascular collapse, and death.
Prompt administration of antitoxin is necessary to enable it to bind to and de-activate the free toxin in serum. Antitoxin cannot de-activate toxin once it has entered cells, which is signalled by the presence of mucocutaneous symptoms.
Patients with respiratory diphtheria are placed in respiratory isolation (masks and standard measures such as hand-washing), and those with cutaneous diphtheria are placed in contact isolation (gloves and gowns), until cultures taken after cessation of therapy are negative.
Asymptomatic carriers play an important role in disease transmission.
Respiratory diphtheria is an upper-respiratory tract illness characterised by sore throat, low-grade fever, and an adherent pseudomembrane that can cover the tonsils and the mucosa of the pharynx, larynx, and nose. Occasionally, the mucosa of the eyes, ears, or genitals may also be affected. It is caused by exotoxin-producing strains of Corynebacterium diphtheriae. Rarely, it may also be caused by other corynebacteria that produce diphtheria toxin, such as C ulcerans or C pseudotuberculosis. The toxin causes tissue necrosis and formation of the pseudomembrane. It also causes the major complications of myocarditis and neuritis.
Cutaneous diphtheria may be caused by toxigenic or non-toxigenic strains of C diphtheriae and is usually a mild disease, causing cutaneous sores or shallow ulcers. Toxic complications are rare in cutaneous disease, occurring in 1% to 2% of infections with toxigenic strains.
History and exam
Key diagnostic factors
- typical age group (<15 years or >25 years)
- exposure to infected individual
- travel to endemic regions
- unvaccinated/inadequately vaccinated individuals
- sore throat
- dysphagia or dysphonia
- croupy cough
- pseudomembrane formation
- swelling of the neck
- skin lesions
- respiratory compromise
Other diagnostic factors
- low-grade fever
- unvaccinated individuals
- inadequately vaccinated individuals
- exposure to an infected individual
- travel to endemic areas
- skin breakdown
- poor hygiene, overcrowding, and poverty
1st investigations to order
- bacteriological culture and microscopy
Investigations to consider
- Elek test for toxigenicity
- 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, 2022
- Child and adolescent immunization schedule: recommendations for ages 18 years or younger, United States, 2022
DTP vaccine (diphtheria, tetanus, polio)
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