Impetigo Differential Diagnoses

Updated: May 04, 2016
  • Author: Lisa S Lewis, MD; Chief Editor: Russell W Steele, MD  more...
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DDx

Diagnostic Considerations

Alternative diagnostic possibilities are key to consider in recurrent cases or those that do not respond quickly to treatment. Tinea is a very common and often missed mimic. Careful and full skin examination is required to rule out tinea as a cause of impetigo-like infection of the skin. [30, 31] Unlike impetigo, tinea almost never occurs on the upper lip. [32]

Herpetic impetigo also is a very common and often missed mimic. Viral culture is recommended in atopic patients, who are the high-risk group for this presentation. In particular, those patients with extensive eczema are most at risk and should be considered for this testing. [33]

Pemphigus vulgaris is rare in children. Pemphigus foliaceus is both a clinical and histologic mimic of impetigo and normally presents in adults. Folliculitis is a superficial hair follicle infection that produces little interfollicular change or erythema of the skin. This infection site is also rarely tender; if this diagnosis appears possible, the clinician should also consider pseudomonas folliculitis.

Follicular mucinosis can be especially similar to impetigo in clinical presentation, although often without crust. However, in the facial region, distinction between these 2 disorders is difficult without a biopsy. [34] Such mimicry emphasizes the need for early bacterial culture. Recalcitrant presentations may require fungal culture and biopsy. Furuncle is a deeper hair follicle infection with pus and small abscess. It is a more extreme version of folliculitis.

Erysipelas is a skin infection typically caused by group A beta-hemolytic streptococci, as are many cases of nonbullous impetigo. However, erysipelas manifests as a sharply demarcated erythematous plaque caused by dermal inflammation.

Insect bites may resemble impetigo or may be a site for its development, emphasizing the need for a detailed history. Impetigo in an atypical location, such as the scalp, should warrant investigation for head lice.

Other problems to be considered in the differential diagnosis of nonbullous impetigo include the following:

  • Cutaneous candidiasis
  • Kerion
  • Inflammatory dermatophytosis
  • Dermatophytic Infections
  • Discoid lupus erythematosus
  • Sweet syndrome (acute febrile neutrophilic dermatosis)

Other problems to be considered in the differential diagnosis of bullous impetigo include the following:

  • Linear immunoglobulin A bullous dermatosis
  • Bullous pemphigoid reactions
  • Bullous lupus erythematosus
  • Bullous scabies
  • Dermatitis herpetiformis
  • Bullous-fixed drug reaction

Differential Diagnoses