Diphtheria

Pathology

Corynebacterium diphtheria, a gram-positive rod, is the causative agent of diphtheria. The incubation period for this disease ranges from one to five days and it induces the formation of a fibrinous pseudomembrane on the pharyngeal mucosa, in addition to an exotoxin which is responsible for the majority of clinical effects.

Aetiology

Diphtheria is mainly spread through respiratory droplets, with the majority of cases occurring in developing countries where immunization is low or nonexistent.

Symptoms

• Insidious onset: Fever, tachycardia, and coryzal symptoms are usually present at the start of the illness.
• Respiratory (commonest): The onset of symptoms associated with the respiratory system occurs slowly, with fever, sore throat (pseudomembranous pharyngitis), nausea, vomiting, dysphagia, and lymphadenitis.
• Cutaneous: Painful ulcerations with an offensive odor may be superinfected with staphylococci or streptococci.

Signs

The signs of diphtheria include lymphadenitis and soft tissue oedema in the neck.

Investigations

Clinical diagnosis with laboratory confirmation from a throat swab is required to diagnose diphtheria.

Treatment

• Conservative: Bed rest is recommended as a conservative measure.
• Medical: The main course of treatment includes diphtheria antitoxin and antibiotics. Early tracheostomy and ventilation may be necessary if there are signs of tracheal obstruction or respiratory muscle paralysis.

Complications

Complications related to diphtheria include laryngeal obstruction, myocarditis, and neuropathy.

Prognosis

The overall mortality rate for diphtheria is roughly 5-10%, with a mortality rate of 50% for cases of myocarditis.

Figure 9.8 Pseudomembrane in diphtheria