Borrelia miyamotoi infection is being reported as a newly recognized tickborne illness, observed in patients originally thought to have human granulocytic anaplasmosis (HGA).

In a case report presented in Annals of Internal Medicine, Hanumara Ram Chowdri, MD, and colleagues explained that the diverse tickborne infections of the northeastern United States can present as undifferentiated flulike illness. When patients in areas known for Lyme disease and other tickborne diseases develop acute febrile illness with myalgia, headache, neutropenia, thrombocytopenia and elevated hepatic aminotransferase levels, they often are presumed to have HGA.

Two patients with fever presented to primary-care medical centers, one in Massachusetts and one in New Jersey. They each received a diagnosis of HGA but did not respond quickly to doxycycline therapy, nor was there any laboratory evidence of Anaplasma phagocytophilum infection.

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Polymerase chain reaction and DNA sequencing led to the detection of B. miyamotoi in the peripheral blood of both patients. No evidence of infection with other tickborne pathogens common to the area was found, although Chowdri’s team noted that one of the patients may have had concurrent Lyme disease.

The authors advised that clinicians should carefully analyze samples from tick-exposed patients who have acutely presented with signs of HGA but who have a delayed response to doxycycline or negative confirmatory test results for HGA. These patients may in fact be infected with B. miyamotoi.


  1. Chowdri HR et al. “Borrelia miyamotoi Infection Presenting as Human Granulocytic Anaplasmosis: A Case Report.” Ann Intern Med. 2013;159(1):21-27.