Relative Bradycardia in a 61-Year-Old Male With Anaplasmosis: A Case Report.

Human granulocytic anaplasmosis (HGA), or anaplasmosis, is a tick-borne illness caused by Anaplasma phagocytophilum, a gram-negative intracellular bacterium. A. phagocytophilum is primarily transmitted by Ixodes scapularis in the northeast United States and by Ixodes pacificus in California. Presenting symptoms typically include fever, chills, malaise, headache, myalgia, and rarely a rash. This case describes a 61-year-old Black male with a complex medical history, including prior tick-borne and arboviral infections (Lyme disease, dengue fever, and chikungunya), hypertension, mixed hyperlipidemia, bilateral carotid artery dissection, gastroesophageal reflux disease, atrial fibrillation with rapid ventricular response, and current tobacco use. This patient presented to an emergency department in upstate New York with a fever, fatigue, constipation, myalgia, and night sweats. Throughout the patient's hospital course, he maintained a state of relative bradycardia. The patient reported that he had returned from Haiti and the Dominican Republic two weeks prior to presentation in the emergency department and received several mosquito bites while abroad. Initial guideline-based empiric treatment was started with doxycycline due to suspicion of tick-borne illness, given his history of Lyme disease and his onset of symptoms while in upstate New York. Treatment was continued to complete a 14-day course after confirming the diagnosis of anaplasmosis by PCR testing of whole blood. After completing treatment with doxycycline, the patient's symptoms resolved completely. This case illustrates a unique finding of relative bradycardia and fever of unknown origin in the context of recent international travel and history of tick-borne and arboviral infections.