Diphtheria

Diphtheria is an infection caused by corynebacterium diphtheriae. The bacterium most commonly infects the upper airways, but can also affect the lower airways, causing croup. Because the widely available dTP vaccine protects against diphtheria, it's very rare in countries with good vaccination coverage.

Clinical features

The bacterium forms a dense, grey pseudomembrane which covers the tonsils. If its severe enough, it can extend to cover the entire tracheobronchial tree. This causes symptoms of tonsillitis and fever. The bacterium also releases diphtheria toxins, which can result in myocarditis or neuropathy.

If the bacterium infects the lower airways (in which case it's called croup), it may cause severe airway obstruction with stridor and cyanosis because the pseudomembrane covers the airways.

Management

Treatment involves a horse-serum-derived antitoxin, antibiotic therapy, and vaccination. If the pseudomembranes cover and obstruct the lower airways, they must be removed by laryngoscopy.‎