Human ehrlichiosis at a tertiary-care academic medical center: Clinical associations and outcomes of transplant patients and patients with hemophagocytic lymphohistiocytosis

Background: Ehrlichiosis is an acute febrile tick-borne disease which can rarely be a trigger for secondary hemophagocytic lymphohistiocytosis (HLH). Methods: We reviewed our experience with Ehrlichia infections at a tertiary-care academic medical center. Results: Over 10 years, 157 cases of ehrlichiosis were identified. Ten patients (6.4%) had infection with E. ewingii, 7(4.5%) of whom were transplant patients as compared to 3(1.9%) non-transplant patients (p =.035). Transplant patients were more likely to have leukopenia and elevated creatinine compared to immunocompetent patients; length of hospital stay and early mortality were not different between the two groups. Ten patients met the HLH-2004 diagnosis criteria, which could be an underestimation of HLH occurrence as most patients were not completely evaluated for these criteria. We calculated the H-Score to find the probability of HLH; 25 patients scored high making the occurrence rate of HLH at least 16%. Ehrlichia-induced HLH patients (N = 25) had more anemia, thrombocytopenia, elevated creatinine and AST. Moreover, they had a significantly longer hospital stay (median 9 days) compared to patients without HLH (median 4 days) (p =.006). Conclusions: Ehrlichia-induced HLH is a potential serious complication with relatively high occurrence rate; patients manifest severe disease with end-organ damage requiring longer hospital stay.