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A 52-year-old man with chronic lymphocytic leukemia returns early from a camping trip in the northeastern United States because he has broken out in “hives.” He states he was hiking with his wife the previous day and began to notice large welts on his arms, legs, and face 4-6 hours after the hike. These welts have increased in number and severity. He states that they are itchy, but denies pain, fever, headache, nausea, and vomiting. Physical examination reveals two insect bites on the man’s arm and several patches of erythema. His WBC count is 41,000/mm³, hemoglobin is 10 g/dL, and platelet count is 125,000/mm³. Differential demonstrates 100% lymphocytes.
What is the most likely underlying pathogenesis of the patient’s “hives”?
A. Allergy to food consumed on the camping trip
B. Indolent chronic lymphocytic leukemia
C. Infection with Borrelia burgdorferi
D. Rapid-onset Rocky Mountain spotted fever caused by Rickettsia rickettsii
E. Scrub typhus caused by Rickettsia tsutsugamushi
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