Out of Season and Out of Pattern: Winter Ehrlichiosis in a Heart Transplant Recipient With Possible Reactivation or Reinfection

Human monocytic ehrlichiosis (HME) is a tick-borne infection caused by Ehrlichia chaffeensis, an obligate intracellular bacterium that infects monocytes and can lead to systemic inflammatory illness. Clinical manifestations typically include fever, malaise, cytopenias, transaminitis, and, in severe cases, neurologic or multiorgan involvement. Although HME is increasingly recognized in immunocompromised hosts, it remains uncommon in solid organ transplant recipients and is rarely reported outside peak seasonal exposure periods. In transplant patients, atypical presentations, baseline hematologic abnormalities, and the possibility of donor-derived or non-vector transmission can obscure the diagnosis and delay appropriate therapy. In addition, reactivation of ehrlichiosis following transplantation remains poorly characterized, with limited data available regarding its pathogenesis, diagnosis, and management. Here, we present a case of presumed reactivation of ehrlichiosis in a heart transplant recipient and discuss the diagnostic and therapeutic challenges associated with HME in immunosuppressed patients.