Case Presentation: Babesiosis, most commonly caused by Babesia microti and transmitted by the Ixodes tick, is one of the predominant tick-borne diseases of Northeast and upper Midwestern United States (1, 2). Clinical manifestations range from asymptomatic infection to severe fulminant disease, with fever being the most common presentation (3). Acute respiratory distress syndrome and disseminated intravascular coagulopathy are common complications but in rare cases babesiosis may lead to hemophagocytic lymphohistiocytosis (HLH) (3, 4). HLH is rare but frequently fatal, can be acquired due to alterations in immune homeostasis. Here we present a case of Babesiosis resulting in splenic infarcts and HLH in Northern Arizona. A 70-year-old female, with no medical history presented to our hospital with fever, chills, night sweats, anorexia, weight loss of 8 lbs and malaise for 5 days. On presentation, she denied sick contacts, noted having a recent dental infection which resolved with antibiotic therapy and a recent travel to Massachusetts and Vermont.In the ED, she was febrile (39 °C), otherwise hemodynamically stable. Physical exam was notable for 2/6 systolic murmur at the aortic site, hepatosplenomegaly and maculopapular rash on the left lateral abdomen. Labs revealed pancytopenia (Hgb 11.3 g/dL, MCV 90.2, RDW 14.3%, WBC 3.1, absolute neutrophil count (ANC) 1.9, platelets 34), total bilirubin 1.4 (direct bilirubin 0.3), ALT 133, AST 192.CT abdomen/pelvis with IV contrast showed hepatosplenomegaly and splenic infarcts. Transthoracic echocardiogram was unremarkable. The patient was admitted for fever of unknown origin and pancytopenia. Empiric doxycycline was started for suspicion of tick-borne illness. Extensive infectious work-up including blood cultures, tick-borne illness serology, EBV, CMV, and hepatitis panel were obtained. Pancytopenia combined with an elevated ferritin of 4335 raised concern for possible HLH (H-score 175, corresponding to 54-75% probability of HLH). Although the patient remained physically stable, she had worsening pancytopenia (Hgb 7.4, WBC 2.2, ANC 0.9, platelet 43, LDH 684, haptoglobin < 14) and did not appear to be responding to the antibiotic regimen.Peripheral blood smear results were pending. Upon further questioning, the patient recalled hiking with her daughter’s dog who had ticks, but she could not confirm being bitten herself. The peripheral blood smear confirmed normocytic anemia, rare, ring formed extracellular and intracellular organisms (Fig. 1). Tick-borne illness panel returned positive for Babeiosis. Doxycycline was switched to Azithromycin and Atovaquone. Bone marrow biopsy was obtained, which showed a single histiocyte with red blood cells and platelets within the cytoplasm, suggestive of hemophagocytosis (Fig. 2).Patient’s symptoms and lab changes stabilized with the change in antibiotic therapy and was discharged home. On follow-up evaluation one month later, she had complete resolution of pancytopenia.

Discussion: This case represents a relatively healthy female in Arizona with travel history to the Northeast, who presented with severe Babesiosis complicated by splenic infarcts and HLH. HLH in adults, represents immune hyperactivation triggered by an autoimmune, malignant, or infectious process (5) and the treatment consists of treating the underlying trigger.

Conclusions: To our knowledge, to date, there are less than 10 cases of Babesiosis and HLH in the literature (4, 6-13), and this is the first case reported in Arizona.

IMAGE 1: Figure 1: Peripheral blood smear showing ring formed extracellular and intracellular organisms.

IMAGE 2: Figure 2: Bone marrow biopsy showing a single histiocyte with red blood cells and platelets within the cytoplasm.