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FeedbackClassic diphtheria is characterized by the formation of a pseudomembrane on respiratory mucous membranes. Initial testing includes CBC and a rapid strep test. A diphtheria culture is usually diagnostic if disease symptoms are present.
Diagnosis
Indications for Testing
- Presence of pseudomembrane
- Pharyngitis with other organ involvement
Laboratory Testing
- CDC diphtheria overview and laboratory testing recommendations
- Initial testing – CBC, rapid strep test
- Diphtheria culture – usually diagnostic if disease symptoms are present
Differential Diagnosis
- Pharyngitis
- Group A Streptococcus
- Epstein-Barr virus
- Viral pharyngitis
- Vincent angina
- Epiglottitis
- Skin lesions
- Psoriasis
- Eczema
- Autoimmune immunobullous disease
- Contact dermatitis
- Bacterial infection
- Streptococcus pyogenes
- Staphylococcus aureus
- Group B Streptococcus
- Cough
Background
Epidemiology
- Incidence – very rare in U.S. due to vaccination
- Age – usually in children <15 years who are unvaccinated or incompletely vaccinated
- Transmission – airborne or direct contact (respiratory secretions or skin lesion)
Organism
- Gram-positive bacillus
- Not spore forming
- Unencapsulated
- Pleomorphic
- Produces exotoxin that causes many of the symptoms
- Results in asymptomatic carriage in some patients
Pathophysiology
- Virulence is mediated by prophage-encoded exotoxin
- Toxin induces dense necrotic coagulum on mucous membranes
- Causes underlying soft-tissue edema
Clinical Presentation
- Incubation period – 2-4 days
- Respiratory tract involvement
- Anterior nasal disease
- Faucial disease – classic membranes on pharynx and tonsils, cervical adenopathy, and fever
- Laryngeal and tracheobronchial disease – hoarseness, dyspnea, stridor, and brassy cough
- Cardiac disease – myocarditis
- Mortality 3-4 times that of patients without cardiac involvement
- Related to toxin release
- Neurologic disease – demyelinating neuropathy
- Usually motor neuropathy
- Related to severity of disease – rare in mild disease
- Renal disease – proteinuria, renal failure
- Cutaneous disease – chronic nonhealing ulcers with dirty gray membrane, often in mixed infections with Staphylococcus aureus and group A streptococci
- Invasive disease
- Endocarditis
- Mycotic aneurysms
- Osteomyelitis
- Septic arthritis
Prevention
Vaccination
ARUP Laboratory Tests
Identify Corynebacterium diphtheriae in clinical specimens
Culture/Identification
Identify infectious process
Automated Cell Count/Differential
Rule out more common cause of pharyngitis
If Streptococcus (Group A) rapid test is negative and patient is ≤18 years, culture will be added for confirmation
Nucleic Acid Amplification
Evaluate the ability of a patient to produce antibody to pure protein vaccines after vaccination to rule out antibody deficiency
Quantitative Multiplex Bead Assay
Evaluate the ability of a patient to produce antibody to pure protein vaccine after vaccination to rule out antibody deficiency
Quantitative Multiplex Bead Assay
Evaluate the ability of a patient to produce antibody to pure protein vaccines (diphtheria and tetanus) and protein conjugated bacterial (Haemophilus influenza) vaccines after vaccination to rule out antibody deficiency
Quantitative Multiplex Bead Assay
Medical Experts
Fisher
References
CDC - Manual for the Surveillance of Vaccine-Preventable Diseases - Chapters
U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. Manual for the surveillance of vaccine-preventable diseases. [Updated: Jun 2020; Accessed: Mar 2021]
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Mokrousov I. Corynebacterium diphtheriae: genome diversity, population structure and genotyping perspectives. Infect Genet Evol. 2009;9(1):1-15.
CDC - Recommended Immunization Schedules for Children and Adolescents Aged 18 Years or Younger
U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. Advisory Committee on Immunization Practices recommended immunization schedule for children and adolescents aged 18 years or younger – United States, 2019. [Last updated: Feb 2019; Accessed: Sep 2020]