Impetigo

Background and Epidemiology

  • Common and highly contagious pyogenic infection of the epidermis
  • Two forms: common non-bullous form and uncommon bullous form.  It can also be classified as primary (i.e. previously normal skin) or secondary (i.e. previous dermatological condition or breach of the skin)
  • Mainly a disease of childhood
  • Incidence of around 2.8% of children <4 years old and 1.6% of children 5-15 years old

Aetiology and Microbiology

  • Most commonly due to infection with Staphylococcus aureus (almost always the cause of bullous impetigo) but can occasionally be due to β-haemolytic streptococcus e.g. Streptococcus pyogenes or a mix
  • There are not many risk factors except for contact with another infected individual.  Skin hygiene may or may not be important.

Presentation

  • In non-bullous disease, impetigo typically presents initially as itchy/uncomfortable vesicle which rapidly ruptures and oozes serous fluid which typically dries to form a ‘golden’ coloured crust over an erythematous base. (~2cm)  These lesions aren’t usually painful or itchy
    • In bullous disease, intact blisters filled with a clear-cloudy fluid develop and burst after 2-3 days.
  • Typical sites of impetigo include the face and truck (classically around the mouth and nostrils in children).  In bullous disease, presentation is usually in axillae, neck folds, nappy area etc.  Occasionally, lesions can appear elswhere due to autoinnoculation
    • Lesions can be multiple and coalesce

Investigations/Diagnosis

  • Diagnosis is usually clinical
  • Skin swabs (for culture/sensitivity) may be necessary in patients with extensive/severe disease, recurrent disease, in the context of an outbreak, suspected MRSA infection

Management

  • Topical Fusidic Acid
  • It may be good to cleanse, remove crust and apply wet dressings
  • For severe disease, consider systemic flucloxacillin
  • For patients with confirmed MRSA impetigo, mupirocin can be used (consult local protocols)
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