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Anaplasmosis encephalitis and infection of non-myeloid bone marrow precursors
  1. Zahra Sohani1,
  2. Nan Zhao2,
  3. Karl Weiss2 and
  4. Hans Knecht3
  1. 1McGill University Health Centre, Montreal, Quebec, Canada
  2. 2Department of Medicine, Jewish General Hospital, Montreal, Quebec, Canada
  3. 3Department of Medicine, McGill University, Montreal, Quebec, Canada
  1. Correspondence to Dr Hans Knecht; hans.knecht{at}


Due to climate change, infections from tickborne pathogens are becoming more prevalent in the Northern Hemisphere. Human granulocytic anaplasmosis, caused by the obligate intracellular gram-negative bacteria Anaplasma phagocytophilum and carried by Ixodes ticks, can lead to morbidity and mortality in select populations. Anaplasmosis is commonly accompanied by significant cytopaenia, the pathophysiology of which remains unknown. Our case report describes an uncommon meningoencephalitic presentation of anaplasmosis with substantial anaemia and thrombocytopaenia. Additionally, we propose a mechanism of bone marrow infection and suppression by A. phagocytophilum which may be responsible for the cytopaenia in anaplasmosis and provide pictographic evidence of anaplasma in peripheral blood, cerebrospinal fluid and bone marrow.

  • Haematology (incl blood transfusion)
  • Infectious diseases

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  • Contributors The following authors were responsible for drafting of the text, sourcing and editing of clinical images, investigation results, drawing original diagrams and algorithms, and critical revision for important intellectual content: ZS, NZ, KW and HK. The following authors gave final approval of the manuscript: ZS, NZ, KW and HK. Is the patient one of the authors of this manuscript? No.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.