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Key Features

Essentials of Diagnosis

  • Gray, adherent pseudomembrane, most often in the pharynx but also in the nasopharynx or trachea

  • Sore throat, serosanguinous nasal discharge, hoarseness, and fever in a nonimmunized child

  • Peripheral neuritis or myocarditis

  • Positive culture

  • Treatment should not be withheld pending culture results

General Considerations

  • Defined as an acute infection of the upper respiratory tract or skin caused by toxin-producing Corynebacterium diphtheriae

  • In immunized communities, infection probably occurs through spread of the phage among carriers of susceptible C diphtheriae rather than through spread of phage-containing bacteria themselves

  • Diphtheria toxin kills susceptible cells by irreversible inhibition of protein synthesis

  • Toxin is absorbed into the mucous membranes and causes destruction of epithelium and a superficial inflammatory response

  • Necrotic epithelium becomes embedded in exuded fibrin with WBCs and RBCs (red blood cells), forming a grayish pseudomembrane over the tonsils, pharynx, or larynx

  • Incubation period is 2–7 days


  • Disease is rare in the United States; five cases have been reported since 2000; none since 2003

  • However, significant numbers of elderly adults and unimmunized children are susceptible to infection

  • Occurs in epidemics in countries where immunization is not universal

  • Unimmunized travelers to these areas may acquire the disease

Clinical Findings

Symptoms and Signs

  • Pharyngeal diphtheria

    • Early manifestations are mild sore throat, moderate fever, and malaise, followed fairly rapidly by prostration and circulatory collapse

    • Pulse is more rapid than the fever would seem to justify

    • A pharyngeal membrane forms

      • May spread into the nasopharynx or the trachea, producing respiratory obstruction

      • Tenacious and gray

      • Surrounded by a narrow zone of erythema and a broader zone of edema

    • The cervical lymph nodes become swollen, which is associated with brawny edema of the neck (so-called bull neck)

  • Laryngeal diphtheria presents with stridor, which can progress to airway obstruction

  • Cutaneous, vaginal, and wound diphtheria

    • Account for up to one-third of cases

    • Characterized by ulcerative lesions with membrane formation

Differential Diagnosis

  • Pharyngeal diphtheria resembles pharyngitis secondary to

    • β-Hemolytic streptococcus

    • Epstein-Barr virus

    • Other viral respiratory pathogens

  • A nasal foreign body or purulent sinusitis may mimic nasal diphtheria

  • Other causes of laryngeal obstruction include epiglottitis and viral croup

  • Guillain-Barré syndrome, poliomyelitis, or acute poisoning may mimic the neuropathy of diphtheria


  • Clinical

  • Direct smears are unreliable

  • Cultures

    • Material is obtained from the nose, throat, or skin lesions

    • Specialized culture media are required

    • Between 16 and 48 hours are required before identification of the organism

    • May be negative in individuals who have received antibiotics

  • A toxigenicity test is performed

  • WBC count usually is normal

  • Hemolytic anemia and thrombocytopenia are common


General Measures

  • Obervation of patients in the hospital ...

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