Review Question - QID 109856

A 32-year-old man presents to his nearby clinic for a non-healing and painful leg ulcer. The sore started approximately 3 weeks ago as a tender nodule. He first noticed the bump after hitting his shin during a soccer game. The lesion later “opened up” into an ulceration. The patient also complains of lower back pain and intermittent diarrhea for the past 4 months. The patient’s medical history is non-significant except for chlamydia for which he was successfully treated. He uses acetaminophen for back pain but takes no other medications. The patient is sexually active with 2 male partners. He smokes marijuana daily. He reports he recently returned from his summer volunteering at a children’s soccer program in Uganda. While there he reports getting bitten by mosquitos and taking anti-malarial medication as prescribed. Physical examination shows limited spine flexion and a lesion as pictured in Figure A. Labs are drawn and are shown below:

Hemoglobin: 10.9 g/dL
Leukocyte count: 10,800/mmm^3
Platelet count: 320,000/mm^3

Urinalysis:
Protein: Negative
Blood: Negative
Nitrites: Negative
Bacteria: None
White blood cells: 1-2/hpf
Red blood cells: 3-5/hpf

Stool cultures are negative. Which of the following is the most likely diagnosis?