INTRODUCTION

Diphtheria is an infectious disease caused by the gram-positive bacillus Corynebacterium diphtheriae. Infection may lead to respiratory disease, cutaneous disease, or an asymptomatic carrier state. The word diphtheria comes from the Greek word for leather, which refers to the tough pharyngeal membrane that is the clinical hallmark of infection.

The diagnosis and treatment of diphtheria will be reviewed here. The epidemiology, pathophysiology, clinical manifestations, and prevention of this infection are discussed separately. (See "Epidemiology, pathophysiology and clinical manifestations of diphtheria" and "Standard immunizations for children and adolescents", section on 'Diphtheria, tetanus, and/or pertussis vaccines' and "Tetanus-diphtheria toxoid vaccination in adults".)

DIAGNOSIS

The diagnosis of diphtheria should be considered in the setting of relevant clinical manifestations (sore throat, malaise, cervical lymphadenopathy, and low grade fever) together with appropriate epidemiologic risk factors. Mild pharyngeal erythema typically progresses to areas of white exudate; these coalesce to form an adherent gray pseudomembrane that bleeds with scraping. Clinical suspicion for diphtheria should be further heightened in the setting of adherent pharyngeal, palatal, or nasal membranes, systemic toxicity, hoarseness, stridor, palatal paralysis, and/or serosanguineous nasal discharge [1]. (See "Epidemiology, pathophysiology and clinical manifestations of diphtheria", section on 'Clinical manifestations'.)

Definitive diagnosis of diphtheria requires culture of C. diphtheriae from respiratory tract secretions or cutaneous lesions, and a positive toxin assay. Routine laboratory results are usually non-specific and may include a moderately elevated white blood cell count and proteinuria.

Culture — Cultures should be obtained from the throat and nose including a portion of the membrane (if possible), and material from beneath the membrane [2]. Special culture media (Loffler's or Tindale's) are required; the microbiology laboratory should be notified of the suspected diagnosis so that the specimen is plated on appropriate media. Transport to the laboratory must be accomplished quickly since the media must be inoculated promptly [2].