Neoehrlichia mikurensis - an emerging opportunistic tick-borne infection in immunosuppressed patients

Rosa M M Gynthersen*, Christen Rune Stensvold, Signe Ledou Nielsen, Holger Jon Møller, Henrik Vedel Nielsen, Anne-Mette Lebech, Jeppe Romme Christensen, Helene Mens, Daniel El Fassi

*Corresponding author for this work


BACKGROUND: Neoehrlichia mikurensis (N. mikurensis) is a newly discovered tick-borne pathogen that can inflict life-threatening illness in immunocompromised patients. N. mikurensis infection is only detectable by polymerase chain reaction (PCR)-based methodologies. We describe three distinct clinical manifestations of N. mikurensis infection (neoehrlichiosis) in Danish patients receiving B-lymphocyte-depleting therapy, rituximab, for underlying hematological, rheumatological, or neurological disorders. All three patients went through a protracted pre-diagnostic period.

METHODS: N. mikurensis DNA was detected and confirmed using two methods. Blood was tested by specific real-time PCR targeting the groEL gene and by 16S and 18S profiling followed by sequencing. Bone marrow was analyzed by 16S and 18S profiling.

RESULTS: N. mikurensis was detected in blood samples in all three cases and in bone marrow from one of the three. The severity of the symptoms ranged from prolonged fever lasting more than 6 months to life-threatening hyperinflammation in the form of hemophagocytic lymphohistiocytosis (HLH). Interestingly, all patients presented with splenomegaly and two with hepatomegaly. After starting doxycycline therapy, symptoms were relieved within a few days, and biochemistry and organomegaly quickly normalized.

CONCLUSION: We present three Danish patients recognized by the same clinician over a period of 6 months, strongly suggesting that many cases are going unrecognized. Second, we describe the first case of N. mikurensis-induced HLH and emphasize the potential severity of undetected neoehrlichiosis.

Original languageEnglish
JournalJournal of Internal Medicine
Issue number6
Pages (from-to)782-790
Number of pages9
Publication statusPublished - Jun 2023


Dive into the research topics of 'Neoehrlichia mikurensis - an emerging opportunistic tick-borne infection in immunosuppressed patients'. Together they form a unique fingerprint.

Cite this