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Rash on back

A 7-year-old girl came into our office with a widespread rash on her back and buttocks. Her mother reported that the rash started 3 days ago and she was concerned because it appeared to be spreading. The child did not appear ill, but said the rash was uncomfortable.

What's your diagnosis?


This patient had impetigo. The honey crusted erythematous lesions are typical for this superficial bacterial skin infection. Impetigo is caused by Staphylococcus aureus and/or group A beta-hemolytic Streptococcus (GABHS). The differential diagnosis for this case included herpes simplex, tinea corporis, and superinfected atopic dermatitis.

There is good evidence that topical mupirocin is equally or more effective than oral treatment for people with limited impetigo. Mupirocin also covers methicillin-resistant Staphylococcus aureus. Extensive impetigo should be treated for at least 7 days with antibiotics that cover group A beta-hemolytic Streptococcus and S aureus.

We treated our patient with oral cephalexin 35 mg/kg/day and the impetigo was resolved at a 2-week follow-up visit. The culture grew out S aureus sensitive to cephalosporins.

This case was adapted from: Usatine R. Impetigo. In: Usatine R, Smith M, Mayeaux EJ, Chumley H, Tysinger J, eds. The Color Atlas of Family Medicine. New York, NY: McGraw-Hill; 2009:461-465.

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