Severe human monocytic ehrlichiosis presenting with altered mental status and seizures

A previously healthy 66-year-old woman living in the Mid-Atlantic USA presented to the hospital with lethargy, ataxia and slurred speech. 2 weeks prior she had removed a tick from her right groin. She reported malaise, fevers, diarrhoea, cough and a rash. Physical examination revealed a maculopapular rash on her chest, and lung auscultation revealed bi-basilar rales. Laboratory tests were remarkable for hyponatraemia, leucopenia and thrombocytopenia. Chest X-ray demonstrated bilateral pleural effusions with pulmonary oedema. She was treated with ceftriaxone and azithromycin for possible community-acquired pneumonia but declining mental status necessitated intensive care unit transfer. Vancomycin and doxycycline were added. Her course was complicated by seizures requiring antiepileptic therapy. Peripheral blood smear demonstrated morulae in monocytes. Serum Ehrlichia chaffeensis DNA was positive confirming the diagnosis of human monocytic ehrlichiosis. She recovered without residual neurological deficits after 10 days of doxycycline therapy.