Back to Basics: A common rash

12 yo male with no significant pmh presents to the ED with a progressive rash on his feet over the past week. Afebrile and hemodynamically stable. No improvement with topical mupirocin and PO Clindamycin. Derm photos below. Diagnosis? Treatment plan?




Bullous impetigo 




Bullae and/or blisters, clear-yellow fluid that turns dark, leaves yellow crust when rupture 



-- Staph aureus (MSSA or MRSA) - Epidermolytic toxin A and B act locally to cause blisters 

-- Also consider Strep pyogenes (GAS)



Spontaneous resolution in 2-3 weeks OR ...


Antibiotic options:

Mupirocin 2%

TID for 14 days 



25–50 mg/kg/24 hr PO ÷ Q6–12

MSSA or strep 


10–40 mg/kg/24 hr ÷ Q6–8 hr;  max. dose: 1.8 g/24 hr

MRSA and strep



8–12 mg/kg/24 hr ÷ BID;  max. dose: 160 mg/dose

MRSA, poor strep


≤45 kg:  2.2–4.4 mg/kg/24 hr once daily–BID PO/IV 

>45 kg:  100–200 mg/24 hr ÷ once daily–BID PO/IV 

Max. dose:  200 mg/24 hr

MRSA, poor strep


15 mg/kg Q6h




Hartman-Adams H, Banvard C, Juckett G. Impetigo: Diagnosis and Treatment. Am Fam Physician. 2014 Aug 15;90(4):229-35.

Bonfante G, Dunn A. Rashes in Infants and Children. In: Tintinalli JE, Stapczynski J, Ma O, Yealy DM, Meckler GD, Cline DM. eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8e New York, NY: McGraw-Hill; 2016.

Lee CK. Drug Dosages. In: Hughes HK, Kahl LK. The Harriet Lane Handbook, 21e, 2018