Diphtheria

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

Demographics

• 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

Diagnosis

• 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

Treatment

General Measures

• Obervation of patients in the hospital for 10–14 days is usually required

• All patients must be ...