Overview
Diphtheria is an infection due to the Gram-positive rod, Corynebacterium diphtheriae, often leading to an infection of the pharynx. A key feature includes the presence of a pseudomembrane at the site of infection and it produces the diphtheria toxin which can cause systemic effects including myocarditis and polyneuritis.
Pathophysiology
Corynebacterium diphtheriae spreads via nasopharyngeal secretions and can survive for months in fomites. It produces an exotoxin which can inhibit protein synthesis, resulting in toxic effects on the heart, nerves, and kidneys. Tissue destruction caused by this toxin results in the formation of a fibrous pseudomembrane, usually on the respiratory mucosa. Once absorbed into the blood, it causes necrosis of distal tissues.
Epidemiology
- Incidence is highest in young children >3 months old due to the waning of protective maternal antibodies
- Diphtheria is rare in the UK, with around 10 reported cases per year, but is more common in developing countries including Eastern Europe, Russia, and Asia
Risk Factors
- Unvaccinated/inadequately vaccinated
- Exposure to someone with infection
- Travel/living in an endemic area
Presentation
Features of diphtheria include:
- Sore throat and a diphtheric membrane – commonly seen and found on the tonsils due to tissue destruction
- Bulky cervical lymphadenopathy – ‘bull neck’ appearance, due to the spread of toxin to the lymph nodes, may cause breathing difficulties (e.g. stridor)
- Neurologic complications – weakness/paralysis due to demyelination
- Cardiac complications – myocarditis, heart block due to tissue damage
Investigations
Overview
A throat swab culture is a key diagnostic test and identifies the presence of Corynebacterium diphtheriae.
Investigations
culture of throat swab: uses tellurite agar or Loeffler’s media
Management
Overview
Management involves intramuscular penicillin and diphtheria antitoxin.
