Presentation depends on sites of infection: anterior nasal, tonsillar/pharyngeal, laryngeal, cutaneous, ocular or genital. Any mucosal site can be involved.

Symptomatic infection results from 2 factors:

• Local non-invasive inflammation of the respiratory tract or skin; and
• Local and systemic effects of a potent diphtheria exotoxin.

Tonsillar/pharyngeal

• Sore throat, fever and malaise.
• Thick greyish pseudomembrane on tonsils extending to soft palate.
• Cervical lymphadenopathy and oedema (“bull neck”).

Laryngeal

• Can be direct extension from pharyngeal form or the only site of involvement.
• Fever, hoarseness, barking cough
• Can lead to airway obstruction, coma, death

Cutaneous diphtheria

• Primary chronic, non-healing ulcers with a dirty gray membrane
• Systemic toxicity is rare.
• Diphtheritic skin infection induces a brisk antibody response and is therefore immunizing.

Potential complications

Absorption and dissemination of the toxin leads to remote complications like myocarditis, endocarditis, neuritis, otitis media, respiratory compromise and death.

• Throat and nasopharyngeal swabs: need to alert laboratory to suspected diagnosis so that selective culture media can be used (Loffler's or Tindale's).
• ECG to detect conduction block.

A legally notifiable disease in Singapore. Notify Ministry of Health (Form MD 131 or electronically via CD-LENS) not later than 72 hours from the time of diagnosis.

• Antitoxin should be administered without delay if the diagnosis is seriously suspected (dose 20,000 - 100,000 units depending on severity).
• Procaine penicillin G 25,000 to 50,000 units/kg per day for children and 1.2 million units/day for adults given IM in two divided doses.
• Erythromycin (40 to 50 mg/kg per day, up to a maximum of 2 grams/day IV) is recommended until the patient can swallow comfortably. At that point, oral penicillin V (125 to 250 mg four times daily) can be used.
• Respiratory isolation (for pharyngeal/laryngeal diphtheria) until 2 negative cultures (taken 24 hours apart) after stopping antibiotics.
• Patients should be given diphtheria toxoid immunisation since infection does not confer immunity.
• Patients who continue to harbour the organism after treatment should receive  an additional 10-day course of oral erythromycin and should submit samples for follow-up cultures.

Management of close contacts

• Take cultures from throat and nasal swabs.
• Prophylactic antibiotics with either penicillin or erythromycin.
• A single dose of benzathine penicillin G (600,000 units IM for persons <6  years of age and 1.2 million units IM for persons ≥6 years of age) or a 7 to 10- day course of oral erythromycin (40 mg/kg per d for children and 1 g/d for adults) has been recommended.
• Immunization or booster shots depending on immunization history.
• Antitoxin if contacts develop signs and symptoms of diphtheria.

• Respiratory isolation of suspected pharyngeal/laryngeal cases.
• Routine childhood vaccination: primary immunisation at 3, 4 and 5 months (DPT); first booster (DPT) before school entry at 18 months, with a second booster (either Td or Tdap) at 10-11 years (Primary V). See Appendix 2.
• Notification of all childhood immunisations to the National Immunisation Registry, Health Promotion Board, and post-vaccination adverse reactions to the Pharmacovigilance Branch, Health Sciences Authority.

• Countries with endemic diphtheria include Asia/Oceania – Afghanistan, Bangladesh, Cambodia, China, India, Indonesia, Iran, Iraq, Laos, Mongolia, Burma (Myanmar), Nepal, Pakistan, Philippines, Syria, Thailand, Turkey, Vietnam, and Yemen; Africa – Algeria, Egypt, and the countries in sub- Saharan region; Americas – Brazil, Dominican Republic, Ecuador, and Haiti; and Europe – Albania and all countries of the former Soviet Union.
• Adults travelling to endemic areas should receive booster Td vaccine if their vaccination has lapsed for more than 10 years.