Approach to peripheral lymphadenopathy Quiz: Ace Your Exams

A 28-year-old woman presents to the clinic due to recurrent fevers and a painful lump in her right axilla for the past three weeks. She recently went on a camping trip to a lake in New Hampshire. She works in a daycare, and many children have been sick recently. She has a cat and a dog at home. She remembers having a red papule on the upper arm about a week before when the axillary lump appeared. Temperature is 38.3 °C (100.9 °F), blood pressure is 112/72 mmHg, heart rate is 106 beats/minute, respiratory rate is 14 breaths/minute, and oxygen saturation is 100% on room air. On examination, several tender, enlarged lymph nodes are palpable in the right axillary region. The rest of the physical examination is pending. Which of the following is the most likely diagnosis?