TITLE:
Expanding the Clinical Spectrum of Anaplasmosis: A Case of Meningitis Due to Anaplasma phagocytophilum
AUTHORS:
Robert Snedegar, Ryan Wanstreet, Ethan Weneck
KEYWORDS:
Anaplasmosis, Meningitis, Tickborne Disease
JOURNAL NAME:
Case Reports in Clinical Medicine,
Vol.14 No.11,
October
29,
2025
ABSTRACT: Human Granulocytotropic Anaplasmosis (HGA), caused by Anaplasma phagocytophilum, is a tickborne illness typically characterized by acute febrile illness, headache, malaise, thrombocytopenia, leukopenia, and elevated hepatic transaminases. Central Nervous System (CNS) involvement is not recognized as a clinical manifestation of HGA, and meningitis is particularly rare. We report an unusual case of anaplasmosis presenting with clinical and laboratory findings consistent with meningitis. A 68-year-old woman with a history of extended-spectrum beta-lactamase urinary tract infection presented with headache, fever, polyuria, and low back pain. Initial evaluation revealed stable vital signs, mild pyuria, and normal complete blood count and metabolic panel. On hospital day two, she developed fever to 101.2˚F, thrombocytopenia (platelets 117,000/µL), and altered mental status. A Giemsa stain showed toxic changes in granulocytes, but no other significant abnormalities. Despite extensive evaluation, no etiology was identified. Her neurologic status deteriorated on day three, with encephalopathy, diaphoresis, and nystagmus. Lumbar puncture revealed elevated protein (191 mg/dL), mild hypoglycorrhachia (59 mg/dL), and pleocytosis (391 nucleated cells/µL). Empiric broad-spectrum antimicrobials were initiated. Infectious disease consultation recommended PCR testing for tickborne pathogens, which was positive for Anaplasma phagocytophilum. Vancomycin, ceftriaxone, and acyclovir were discontinued, and the patient was treated with doxycycline 100 mg twice daily for 14 days, resulting in rapid improvement in mental status, platelet count, and inflammatory markers. She was discharged home without sequelae. This case expands the recognized clinical spectrum of HGA by demonstrating meningitis as a potential presentation. Clinicians should consider anaplasmosis in the differential diagnosis of meningitis in endemic areas, as timely initiation of doxycycline is associated with rapid recovery and favorable outcomes.