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USMLE® Step 1 questions

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USMLE® Step 1 style questions USMLE

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A 17-year-old young man presents to his primary care physician for evaluation of lesions on the abdomen. The lesions were fluid-filled sacs that eventually burst, leaving behind yellow, crusted areas of inflammation. The patient is otherwise healthy and does not take any medications. Temperature is 37.7°C (99.9°F), blood pressure is 112/73 mmHg, and pulse is 68/min. Physical examination is notable for the following finding:

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Which of the following pathogenic factors is most likely responsible for this patient’s clinical presentation?  

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Bullae p. 487

impetigo p. 491

Bullous impetigo p. 491

Crust (skin) p. 487

impetigo p. 491

Impetigo p. 487

crusts with p. 491

Streptococcus pyogenes p. , 134

sunburn and p. 496


Impetigo is a highly contagious skin infection that is most commonly caused by Group A streptococcus and Staphylococcus aureus bacteria. These bacteria often inhabit the skin and mucous membranes without causing any problems, but under certain conditions they can cause impetigo.

The hallmark sign of impetigo is the presence of honey-colored crusts on the skin. The lesions may be small or large, and may occur anywhere on the body. Impetigo may be accompanied by systemic symptoms such as fever, malaise, and swollen lymph nodes.


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