Diphtheria

• Nature of Disease: Acute, primarily affecting the upper respiratory tract.
• Historical Impact: Historically caused substantial mortality.
• Reduction in Cases: Widespread vaccination has led to its virtual disappearance in many regions.

Resurgence and Current Risk

• 1990s Resurgence: Epidemic diphtheria re-emerged in the former Soviet Union due to disrupted vaccination programs.
• Spread: Cases also occurred in neighboring European countries and among travelers to these regions.
• Current Risk Areas:
  • Southeast Asia
  • New Guinea
  • States of the former Soviet Union
  • Baltic countries
  • Eastern European countries

Recent Cases in Developed Countries

• Nature of Cases: Almost all cases in developed countries are now associated with imported infections.
• Cases in Australia:
  • Over 20 cases reported since 2015.
  • Notable deaths in unvaccinated individuals in 2011 and 2018.

History and Physical

• Initial Presentation: Nonspecific flu-like symptoms including fever, sore throat, and cervical lymphadenopathy.
• Incubation Period: Generally 2 to 5 days, but can range from 1 to 10 days.
• Travel History: Often linked to travel from endemic regions without vaccination.
• Characteristic Signs:
  • Thick, gray, adherent pseudomembrane over the tonsils and throat.
  • Respiratory tract involvement; begins with mild erythema progressing to coalescing pseudomembrane.
  • Pseudomembrane composition: Red blood cells, white blood cells, dead cell debris, organisms; bleeds if scraped.

Evaluation

• Laboratory Diagnosis:
  • Initial Testing: Gram stain and methylene blue on throat sample; shows club-shaped, non-encapsulated, nonmotile bacilli.
  • Culture: Performed on Loffler medium or Tindale media; identification of black colonies with halos, metachromatic granules.
  • Toxin Testing: Elek test, PCR testing, enzyme immunoassay (EIA) for toxigenic strains.
• Additional Studies:
  • Complete blood count may show moderate leukocytosis.
  • Troponin I for assessing myocardial injury.
  • Imaging: Chest and neck x-ray may show swelling around the pharynx and epiglottis.

Treatment / Management

• Antitoxins and Antibiotics:
  • Immediate administration of diphtheria antitoxin based on clinical assessment.
  • Antibiotics: Erythromycin or penicillin G to eradicate the organism and limit toxin release.
  • Alternative antibiotics: Linezolid or vancomycin in case of resistance.
• Supportive Care:
  • Assessment for respiratory and cardiovascular instability.
  • Isolation and droplet precautions.
  • Airway management if respiratory distress is present.
  • Cardiac monitoring for early detection of complications.

Differential Diagnosis

• Conditions to Differentiate:
  • Epiglottitis: Inflammation involving the supraglottic region.
  • Retropharyngeal Abscess: High spiking fevers, urgent drainage required.
  • Angioedema: Generalized swelling of lower dermis and subcutaneous tissues.
  • Infectious Mononucleosis: Presents with fever, pharyngitis, lymphadenopathy.
  • Pharyngitis: Sudden onset sore throat, fever, odynophagia.
  • Oral Candidiasis: Differentiate grayish pseudomembrane from candidiasis.

Prognosis

• Influencing Factors:
  • Age: Higher mortality in individuals younger than five or older than 40 years.
  • Symptom Onset: Greater mortality if symptoms onset after four days.
  • Cardiac Involvement: Poor prognosis, particularly with AV and left bundle-branch blocks.
  • Systemic Disease: High mortality associated with systemic involvement.

Complications

• Common Complications:
  • Myocarditis: May present with cardiac arrhythmias, heart block, circulatory collapse.
  • Neuritis: Weakness or paralysis involving cranial and peripheral nerves.
• Severe Cases:
  • Respiratory obstruction: May require mechanical ventilation and intubation.
  • Neurological: Encephalitis and other severe neurological outcomes in children.