Derm Dx: Asymptomatic Blisters on a Child's Upper Leg - Clinical Advisor

Derm Dx: Asymptomatic Blisters on a Child’s Upper Leg

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A 7-year-old boy presents with 2 blisters that developed acutely on his upper thigh. According to his mother, the lesions began as reddened patches less than 48 hours earlier. The child denied discomfort including itching and pain. He was afebrile and without malaise. Needle puncture of the lesions resulted in drainage of a serosanguineous fluid with slight purulence.

Can you diagnose this condition?

Bullous impetigo is a bacterial skin infection that most commonly affects neonates and children aged <2 years.1,2 The condition is caused by toxin-producing Staphylococcus aureus that disrupts cell adhesion through cleavage of desmoglein-1.3 Bullous impetigo presents with superficial vesicles that...

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Bullous impetigo is a bacterial skin infection that most commonly affects neonates and children aged <2 years.1,2 The condition is caused by toxin-producing Staphylococcus aureus that disrupts cell adhesion through cleavage of desmoglein-1.3 Bullous impetigo presents with superficial vesicles that evolve into enlarging, flaccid bullae with sharp margins and absence of surrounding erythema.  Eventually, these bullae rupture and form yellow-pigmented crusts on the skin.  The presence of a “collarette” scale that surrounds ruptured bullae is described as a pathognomonic finding. 

Bullous impetigo in children is less contagious than the nonbullous variant.4 Diagnosis is usually based on history and examination with confirmation by bacterial culture. Mild cases may be treated with a topical antibiotic such as mupirocin; more extensive cases may warrant oral therapy.

References

  1. Cole C, Gazewood J. Diagnosis and treatment of impetigo. Am Fam Physician. 2007;75(6):859-864.
  2. Johnston G. Treatment of bullous impetigo and the staphylococcal scalded skin syndrome in infants. Expert Rev Anti Infect Ther. 2004;2(3):439-446.
  3. Hanakawa Y, Schechter NM, Lin C, et al. Molecular mechanisms of blister formation in bullous impetigo and staphylococcal scalded skin syndrome. J Clin Invest. 2002;110(1):53-60.
  4. Hirschmann JV. Impetigo: etiology and therapy. Curr Clin Top Infect Dis. 2002;22(22):42-51.
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