Impetigo



Impetigo


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.


TERMINOLOGY


Synonyms



  • Pyoderma


  • Non-bullous impetigo


  • Impetigo contagiosa of Tilbury-Fox


Definitions



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


ETIOLOGY/PATHOGENESIS


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


Pathogenesis



  • 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
Premium Wordpress Themes by UFO Themes
%d bloggers like this: