November 4, 2024

4-year-old boy presents with rash on forearm

By Med-Challenger · 2 minute read

A 4-year-old boy presents with a rash on his forearm. His mother thinks he scraped his arm a few days ago and this rash developed over the area of the abrasion. He is a generally healthy child, on no medications, and up-to-date on immunizations. He attends preschool. He has been afebrile and doesn't report any symptoms other than the rash. The rash is not itchy.

Physical exam is normal, with the exception of a skin lesion on the left forearm. There are several erythematous clustered papules with a golden-colored crust on top.

What is the most appropriate treatment for this patient?

topical acyclovir
topical hydrocortisone
topical mupirocin
oral amoxicillin
topical mupirocin plus oral amoxicillin

The correct answer is:

topical mupirocin

This patient has impetigo. Impetigo is most commonly caused by Staphylococcus aureus or group A beta-hemolytic streptococcal (GAS) species. Children with uncomplicated minor skin infections such as impetigo may be treated with topical mupirocin 2% ointment. Systemic antibiotics are generally not required. Topical hydrocortisone is not an appropriate treatment for infection. Acyclovir is a treatment for herpes virus infection. Herpes lesions tend to appear as groups of vesicles and/or pustules on an erythematous base ("dew drops on rose petals"). Healing herpetic lesions will scab over in contrast to the "honey" crusting seen in impetigo. Herpetic skin lesions requiring antiviral treatment are treated with systemic rather than topical acyclovir.

Impetigo may be caused by methicillin-sensitive or methicillin-resistant S. aureus (MSSA and MRSA, respectively) species in addition to GAS species. All may be effectively treated topically. Some GAS strains may be nephritogenic and more likely to result in post-streptococcal glomerulonephritis than others. There is no evidence that treatment with systemic antibiotics prevents development of post-streptococcal glomerulonephritis, though contacts of patients may be screened for carriage and treated empirically to reduce spread of nephrogenic strains.

Liu et al. Clinical Practice Guidelines by the Infectious Diseases Society of America for the Treatment of Methicillin-Resistant Staphylococcus Aureus Infections in Adults and Children. Clinical Infectious Diseases 2011. 52(3): 285.

2009 Report of the Committee on Infectious Diseases, American Academy of Pediatrics Red Book 27th edition, 2009.

Rudolph, Colin D., editor-in-chief. Rudolph's Pediatrics, 22nd edition. McGraw-Hill 2011.

This question appears in Med-Challenger Pediatric Medicine Exam Review with CME.

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