eMedicine Specialties > Pediatrics: General Medicine > Infectious Disease

Impetigo: Differential Diagnoses & Workup

Author: Lisa S Lewis, MD, Consulting Staff, Division of Emergency Medicine, Children's Hospital Medical Center of Cincinnati
Coauthor(s): Allan D Friedman, MD, MPH, Chairman, Division of General Pediatrics, Dept of Pediatrics, Professor of Pediatrics, Virginia Commonwealth University, VCUH Health System
Contributor Information and Disclosures

Updated: Apr 27, 2009

Differential Diagnoses

Burns, Chemical
Scabies
Burns, Thermal
Varicella
Contact Dermatitis
Herpes Simplex Virus Infection
Pediculosis (Lice)

Other Problems to Be Considered

Other bullous disorders
Stevens-Johnson syndrome
Pemphigus vulgaris
Allergic reactions (erythema multiforme, rhus dermatitis)
Tinea corporis, kerion
Nummular eczema
Linear immunoglobulin A bullous dermatosis
Bullous pemphigoid reactions
Ecchymoses
Dermatitis herpetiformis

Workup

Laboratory Studies

  • Diagnosis of impetigo is usually solely based on history and clinical appearance. Occasionally, confirmation by culture and sensitivity testing of the causative organism may be warranted. Similarly, evidence of previous streptococcal skin infection may be sought in individuals in whom acute glomerulonephritis is suspected.
  • Leukocytosis is present in approximately 50% of patients with impetigo.
  • In patients with nonbullous lesions, after cleansing the honey-colored crusted lesion and uplifting the scab, a bacterial culture of the fresh exudate underneath the scab may be obtained.
  • The following studies may be performed in patients with bullous lesions:
    • Gram stain and culture of the blister fluid reveal many polymorphonuclear WBCs and gram-positive cocci.
    • Bacterial culture yields staphylococci.
  • Documentation of a recent streptococcal skin infection in the differential diagnosis of acute glomerulonephritis is accomplished best by obtaining antideoxyribonuclease B (anti-DNase B) and antihyaluronidase (AH) titers.
    • More than 92% of patients with impetigo-associated APSGN have elevated anti-DNase B titers.
    • Patients with impetigo have a poor antistreptolysin O (ASO) serologic response; only 51% of patients with impetigo-associated poststreptococcal glomerulonephritis develop an increased ASO titer.

Histologic Findings

  • Typical histologic examination of bullous impetigo reveals a blister in the subcorneal or granular region.
  • Polymorphonuclear cells are generally present within the vesicle.
  • Acantholytic cells in the blister cavity, spongiosis, and papillary dermal edema may be present.
  • Bacteria may be observed on Gram stain.
  • Similar findings are present in nonbullous impetigo; however, vesicle formation is significantly smaller.

More on Impetigo

Overview: Impetigo
Differential Diagnoses & Workup: Impetigo
Treatment & Medication: Impetigo
Follow-up: Impetigo
Multimedia: Impetigo
References
Further Reading
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Further Reading

  • The Infectious Diseases Society of America have established practice guidelines for the diagnosis and management of skin and soft-tissue infections. 5

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Keywords

impetigo, impetigo contagiosa, impetigo bullosa, streptococcal impetigo, staphylococcal impetigo, nonbullous impetigo, bullous impetigo, crusted tetter, pyoderma, group A beta hemolytic streptococci, GABHS, Staphylococcus aureus, varicella, acute poststreptococcal glomerulonephritis, APSGN, scarlet fever, osteomyelitis, septic arthritis, pneumonia, septicemia, guttate psoriases, rheumatic fever, treatment, diagnosis, lymphadenopathy

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Contributor Information and Disclosures

Author

Lisa S Lewis, MD, Consulting Staff, Division of Emergency Medicine, Children's Hospital Medical Center of Cincinnati
Lisa S Lewis, MD is a member of the following medical societies: American Academy of Pediatrics
Disclosure: Nothing to disclose.

Coauthor(s)

Allan D Friedman, MD, MPH, Chairman, Division of General Pediatrics, Dept of Pediatrics, Professor of Pediatrics, Virginia Commonwealth University, VCUH Health System
Allan D Friedman, MD, MPH is a member of the following medical societies: American Academy of Pediatrics
Disclosure: Nothing to disclose.

Medical Editor

Glenn J Fennelly, MD, MPH, Director, Division of Pediatric Infectious Diseases, Jacobi Medical Center; Associate Professor, Department of Pediatrics, Albert Einstein College of Medicine
Glenn J Fennelly, MD, MPH is a member of the following medical societies: Pediatric Infectious Diseases Society
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner

Managing Editor

Joseph Domachowske, MD, Professor of Pediatrics, Microbiology and Immunology, Department of Pediatrics, Division of Infectious Diseases, State University of New York-Upstate Medical University
Joseph Domachowske, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Pediatrics, American Society for Microbiology, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, and Phi Beta Kappa
Disclosure: Nothing to disclose.

CME Editor

Robert W Tolan Jr, MD, Chief, Division of Allergy, Immunology and Infectious Diseases, The Children's Hospital at Saint Peter's University Hospital; Clinical Associate Professor of Pediatrics, Drexel University College of Medicine
Robert W Tolan Jr, MD is a member of the following medical societies: American Academy of Pediatrics, American Medical Association, American Society for Microbiology, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, Phi Beta Kappa, and Physicians for Social Responsibility
Disclosure: GlaxoSmithKline Honoraria Speaking and teaching; MedImmune Honoraria Speaking and teaching; Merck Honoraria Speaking and teaching; sanofi pasteur Honoraria Speaking and teaching; Baxter Healthcare Honoraria Speaking and teaching

Chief Editor

Russell W Steele, MD, Head, Division of Pediatric Infectious Diseases, Ochsner Children's Health Center; Clinical Professor, Department of Pediatrics, Tulane University School of Medicine
Russell W Steele, MD is a member of the following medical societies: American Academy of Pediatrics, American Association of Immunologists, American Pediatric Society, American Society for Microbiology, Infectious Diseases Society of America, Louisiana State Medical Society, Pediatric Infectious Diseases Society, Society for Pediatric Research, and Southern Medical Association
Disclosure: None None None

 
 
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