Irina Margaritescu, MD, DipRCPath

Bruce R. Smoller, MD

A case of impetigo demonstrates pustules image, flaccid bullae image, and erosions covered by honey-colored crusts image in a circinate configuration.

This H&E section shows a subcorneal blister with neutrophils image and sparse inflammatory cell infiltrate in the dermis image in a case of bullous impetigo.



  • Pyoderma

  • Non-bullous impetigo

  • Impetigo contagiosa of Tilbury-Fox


  • Acute, contagious, superficial pyogenic infection of skin caused by staphylococci, streptococci, or both


Infectious Agents

  • Staphylococcus aureus (S. aureus)

    • Gram-positive, nonmotile, non-spore-forming, catalase-positive cocci

    • Produce extracellular exfoliative exotoxins (exfoliatin A and B)

  • Streptococcus pyogenes (S. pyogenes)

    • a.k.a. group A β-hemolytic streptococci (GABHS)

    • Gram-positive, nonmotile, chain-forming, non-spore-forming, oxidase- and catalase-negative cocci


  • Staphylococcal pyodermas

    • Occur in individuals who are carriers of organism in axillary, inguinal, and perianal areas and anterior nares

    • Predisposing conditions include atopic dermatitis, diabetes mellitus, dialysis, intravenous drug use, and HIV infection

    • Insect bites, dermatophytoses, herpetic infections, varicella, abrasions, lacerations, and thermal burns also contribute to pathogenesis

  • Group A streptococcal pyodermas

    • Occur following colonization of skin from skin of another individual or from patient’s nasopharynx

  • Non-bullous impetigo

    • Currently S. aureus is prominent pathogen responsible for nonbullous impetigo

      • Accounts for 50-60% of cases

      • In past, S.aureus and S. pyogenes occurred with equal frequency

    • 20-45% of cases are due to combination of S. aureus and S. pyogenes

    • S. pyogenes is still most common cause in developing countries

  • Bullous impetigo

Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Impetigo

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