eMedicine Specialties > Infectious Diseases > Skin and Soft-Tissue Infections

Impetigo: Differential Diagnoses & Workup

Author: John Ratz, MD, MBA, Staff Dermatologist, Mohs Surgeon, Center for Dermatology and Skin Surgery, Inc
Coauthor(s): Daniel B Ward Jr, MD, Clinical Assistant Professor, Department of Dermatology and Dermatologic Surgery, Medical University of South Carolina
Contributor Information and Disclosures

Updated: Nov 5, 2009

Differential Diagnoses

Erythema Multiforme (Stevens-Johnson Syndrome)
Herpes Simplex
Herpes Zoster
Pediculosis
Staphylococcal Infections
Varicella-Zoster Virus

Other Problems to Be Considered

Nonbullous impetigo
Varicella
Tinea corporis
Rhus dermatitis or other contact dermatitis
Nummular eczema
Linear immunoglobulin A bullous dermatosis
Thermal or chemical burns
Pemphigus vulgaris
Bullous pemphigoid
Dermatitis herpetiformis
Bullous-fixed drug reaction
Staphylococcal scalded skin syndrome
Bullous insect bites
Bullous impetigo
Seborrheic dermatitis
Atopic dermatitis
Allergic contact dermatitis
Epidermal dermatophyte infection
Tinea capitis
Scabies
Pediculosis capitis

Workup

Laboratory Studies

  • Impetigo can usually be diagnosed based on the clinical picture.
  • Culture of the involved skin confirms the diagnosis and identifies the causative organism, thereby helping the physician choose appropriate antibiotic therapy.
    • The presence of gram-positive cocci in chains indicates S pyogenes.
    • Gram-positive cocci in clusters indicate S aureus.
    • A culture obtained from intact bullae of bullous impetigo reveals S aureus phage group II.
  • If acute glomerulonephritis presents in a patient with a recent history of impetigo, use a titer of antibodies to streptococcal components (eg, antideoxyribonuclease [DNAse] B, antihyaluronidase, and antistreptolysin O [ASO] titers) to identify a possible etiology for the renal findings.

Histologic Findings

The epidermal cleavage plane is subcorneal in both bullous and nonbullous impetigo. Obtaining biopsies, which is rarely necessary to establish the diagnosis, reveals neutrophils migrating within the epidermis, an inflammatory infiltrate of neutrophils and lymphocytes in the upper dermis, and subcorneal blisters containing occasional acantholytic cells. The blisters of nonbullous impetigo, which are slight and transient, may also contain occasional gram-positive cocci and numerous neutrophils.

More on Impetigo

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

  1. Ludlam H, Cookson B. Scrum kidney: epidemic pyoderma caused by a nephritogenic Streptococcus pyogenes in a rugby team. Lancet. Aug 9 1986;2(8502):331-3. [Medline].

  2. Cunha BA. Antibiotic Essentials. Royal Oak, Mich: Physicians Press:2005.

  3. Dajani AS, Ferrieri P, Wannamaker L. Endemic superficial pyoderma in children. Arch Dermatol. Oct 1973;108(4):517-22. [Medline].

  4. Dajani AS, Ferrieri P, Wannamaker LW. Natural history of impetigo. II. Etiologic agents and bacterial interactions. J Clin Invest. Nov 1972;51(11):2863-71. [Medline].

  5. Dillon HC Jr. Topical and systemic therapy for pyodermas. Int J Dermatol. Oct 1980;DA - 19810424(8):443-51. [Medline].

  6. Drug Information for the Health Care Professional. USP DI-Volume I. 17th ed. Chicago, Ill: Rand McNally; 1997.

  7. el Tayeb SH, Nasr EM, Sattallah AS. Streptococcal impetigo and acute glomerulonephritis in children in Cairo. Br J Dermatol. Jan 1978;98(1):53-62. [Medline].

  8. Elias PM, Levy SW. Bullous impetigo. Occurrence of localized scalded skin syndrome in an adult. Arch Dermatol. Jun 1976;112(6):856-8. [Medline].

  9. Ferrieri P, Dajani AS, Wannamaker LW, et al. Natural history of impetigo. I. Site sequence of acquisition and familial patterns of spread of cutaneous streptococci. J Clin Invest. Nov 1972;51(11):2851-62. [Medline].

  10. Ginsburg CM. Staphylococcal toxin syndromes. Pediatr Infect Dis J. Apr 1991;10(4):319-21. [Medline].

  11. Hay RJ, Adriaans BM. Bacterial Infections. In: Champion RH, Breathnach SM, Burns AD, et al, eds. Textbook of Dermatology. 6th ed. Oxford, England: Blackwell Science; 1998:1097-1179.

  12. Hirschmann JV. Bacterial infections of the skin. In: Sams WM Jr, Lynch PJ, eds. Principles and Practice of Dermatology. 2nd ed. New York, NY: Churchill Livingstone; 1993:79-88.

  13. Hirschmann JV. Topical antibiotics in dermatology. Arch Dermatol. Nov 1988;124(11):1691-700. [Medline].

  14. Kahn RM, Goldstein EJ. Common bacterial skin infections. Diagnostic clues and therapeutic options. Postgrad Med. May 1 1993;93(6):175-82. [Medline].

  15. Lee PK, Weinberg AN, Swartz MN, et al. Pyodermas: Staphylococcus aureus, Streptococcus, and Other Gram-Positive Bacteria. In: Fitzpatrick TB, Eisen AZ, Wolff K, et al, eds. Dermatology in General Medicine. 4th ed. New York, NY: McGraw-Hill; 1999:2182-2207.

  16. Mertz PM, Marshall DA, Eaglstein WH, et al. Topical mupirocin treatment of impetigo is equal to oral erythromycin therapy. Arch Dermatol. Aug 1989;125(8):1069-73. [Medline].

  17. Rice TD, Duggan AK, DeAngelis C. Cost-effectiveness of erythromycin versus mupirocin for the treatment of impetigo in children. Pediatrics. Feb 1992;89(2):210-4. [Medline].

  18. Scales JW, Fleischer AB Jr, Krowchuk DP. Bullous impetigo. Arch Pediatr Adolesc Med. Nov 1997;151(11):1168-9. [Medline].

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Further Reading

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Keywords

impetigo, skin infection, cutaneous infection, bullous impetigo, nonbullous impetigo, Staphylococcus aureus, S aureus, Streptococcus pyogenes, S pyogenes, group A Streptococcus, GAS, group A streptococci, streptococci, staphylococci

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Contributor Information and Disclosures

Author

John Ratz, MD, MBA, Staff Dermatologist, Mohs Surgeon, Center for Dermatology and Skin Surgery, Inc
John Ratz, MD, MBA is a member of the following medical societies: American Academy of Dermatology, American College of Mohs Micrographic Surgery and Cutaneous Oncology, American College of Physicians, American Society for Dermatologic Surgery, American Society for Laser Medicine and Surgery, International Society for Dermatologic Surgery, and Southern Medical Association
Disclosure: Nothing to disclose.

Coauthor(s)

Daniel B Ward Jr, MD, Clinical Assistant Professor, Department of Dermatology and Dermatologic Surgery, Medical University of South Carolina
Daniel B Ward Jr, MD is a member of the following medical societies: American Academy of Dermatology, American Medical Association, and South Carolina Medical Association
Disclosure: Nothing to disclose.

Medical Editor

Gregory William Rutecki, MD, Associate Professor, Program Director, Department of Internal Medicine, Feinberg School of Medicine, Northwestern University
Gregory William Rutecki, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians, American Society of Nephrology, National Kidney Foundation, and Society of General Internal Medicine
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

Gordon L Woods, MD, Consulting Staff, Department of Internal Medicine, University Medical Center
Gordon L Woods, MD is a member of the following medical societies: Society of General Internal Medicine
Disclosure: Nothing to disclose.

CME Editor

Eleftherios Mylonakis, MD, Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital
Eleftherios Mylonakis, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Society for Microbiology, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Chief Editor

Burke A Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital
Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

 
 
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