Case Presentation: A 37-year-old male with no significant past medical history presented to the emergency department (ED) in early October with recurrent fevers, chills, diffuse myalgias, headache, night sweats, and pleuritic midsternal chest pain associated with mild dyspnea. He reported hiking in upstate New York a week prior during late September—a season and region known for tick-borne illnesses—and noted mosquito bites but no apparent tick bites. He was unable to thoroughly check for ticks due to poor weather conditions. Fever (100.8°F) was noted in the ED, though temperatures peaked at 101–102°F on day 1 of admission. He denied gastrointestinal symptoms, rash, photophobia, or urinary complaints, though transient neck stiffness was reported.Initial laboratory studies showed leukopenia (WBC 2.6), thrombocytopenia (platelets 72), and elevated liver enzymes (total bilirubin 1.5, AST 97, ALT 78). He was empirically treated with broad-spectrum antibiotics including vancomycin, piperacillin-tazobactam, and doxycycline, but febrile illness and liver function tests worsened significantly during hospitalization. By days 3 and 4, AST and ALT exceeded 1,000 units/L, though the fever resolved. Workup ruled out viral hepatitis (negative hepatitis A, B, C, and E testing), toxicity from acetaminophen (negative serum acetaminophen level), and other tick-borne infections including Lyme disease and babesiosis (negative PCR). On day 3, Anaplasma PCR returned positive, confirming the diagnosis.Vancomycin and piperacillin-tazobactam were discontinued following PCR confirmation, and doxycycline therapy was continued. Infectious disease specialists noted that severe liver injury with transaminases above 1,000 units/L was a rare complication of anaplasmosis. Transaminases downtrended prior to discharge, and he was sent home to complete a full 7-day course of doxycycline and scheduled for outpatient follow-up to monitor liver function tests.
Discussion: Anaplasma phagocytophilum is a tick-borne pathogen causing anaplasmosis, a febrile illness characterized by nonspecific symptoms, leukopenia, thrombocytopenia, and mild-to-moderate transaminitis. While transaminitis is common, severe liver injury (AST/ALT >1,000 units/L) is exceptionally rare and poorly described in existing literature. This case demonstrates the importance of maintaining clinical suspicion for anaplasmosis even in uncommon presentations of significant hepatic involvement.
Conclusions: Anaplasmosis should be considered in febrile illnesses presenting with cytopenias and transaminitis, even when liver enzymes rise above 1,000 units/L—a rare but potentially severe manifestation. Prompt initiation of doxycycline therapy is critical to prevent complications such as multiorgan failure or worsening hepatic injury. Hospitalists should maintain heightened suspicion for anaplasmosis in endemic regions and ensure thorough follow-up for hepatic recovery after discharge.