Skin-nontumor / Clinical dermatology
Blistering disorders
Impetigo contagiosa

Author: Erin M. Carlquist, M.D. (see Authors page)
Editor: Jerad Gardner, M.D. and Lauren Stuart, M.D.

Revised: 15 June 2016, last major update June 2015

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Impetigo contagiosa [title]

Definition / General
  • Contagious superficial infection of skin
  • Two types of impetigo: impetigo contagiosa (non-bullous impetigo) and bullous impetigo
Epidemiology
  • Non-bullous impetigo comprises > 70% of all cases of impetigo (An Bras Dermatol 2014;89:293)
    • Primarily an endemic disease in school-aged children, but may occur in epidemics
Sites
Etiology
  • In US, most common cause is currently Staphylococcus aureus
  • Previously, most common cause was group A streptococci, either alone or in association with S. aureus (Pediatr Dermatol 1987;4:185)
  • Infection with resistant strains, including methicillin-resistant S. aureus (MRSA) is continually increasing (Pediatr Dermatol 2012;29:243)
Clinical Features
  • Early lesions: easily ruptured vesicopustules on an erythematous base
  • Later lesions: ruptured lesions are replaced by thick, adherent, distinct golden / yellow ("honey-colored") crust
  • Satellite lesions due to self-inoculation are common
Diagnosis
  • Primarily a clinical diagnosis
Laboratory
  • Swab for culture of lesions may rarely be helpful
Prognostic Factors
Case Reports
Treatment
  • Observation is reasonable in uncomplicated infections (Pediatr Dermatol 2012;29:243)
  • Over the counter topical agents include bacitracin and neomycin (Pediatr Dermatol 2012;29:243)
  • Topical disinfectants, including sodium hypochlorite baths, help decrease colonization (Pediatr Dermatol 2012;29:243)
  • Topical antibacterials may minimize resistance and adverse effects from systemic agents (Pediatr Dermatol 2012;29:243); include mupirocin and retapamulin
  • Oral antibacterials are indicated for infection of deeper structures including subcutaneous tissues and muscle fascia (cellulitis), fever, lymphadenopathy, pharyngitis, infections near oral cavity, scalp infections, > 5 lesions (An Bras Dermatol 2014;89:293)
Clinical Images

Images hosted on other servers:

Crusted impetigo

Micro Description
  • Spongiosis of epidermis giving rise to vesicopustules in upper layers of epidermis
  • As lesions progress, epidermis may become eroded and covered with a thick layer of serous crust with neutrophilic debris and Gram positive cocci
  • Superficial dermis displays a moderately dense mixed inflammatory infiltrate
Micro Images

Images hosted on other servers:

Impetigo contagiosa, courtesy of Jerad Gardner, M.D.

Videos




Differential Diagnosis
  • Ecthyma: may be a variant of impetigo but lesions are more punched out, sharply demarcated and result in scarring; also due to superficial bacterial infection usually with Streptococcus pyogenes
  • Secondary impetiginization: similar histologic changes to impetigo may be associated with various other skin conditions; represents secondary infection with cutaneous Gram positive cocci