Neoehrlichiosis associated with arteriovenous fistula thrombosis: a case report

We report on a case of a 55-year-old female with therapy-refractory myasthenia gravis (MG) receiving immunosuppressive treatment and weekly plasma exchange via a stented brachiocephalic arteriovenous fistula. She presented with recurrent thromboses and central stenoses of her arteriovenous fistula, as well as recurrent fever, shivering, malaise, and a localized skin rash. Blood cultures, serological testing, and untargeted next-generation sequencing (NGS) for common pathogens were negative. Histopathology of a skin biopsy demonstrated partial small-vessel thrombosis but no evidence of an infectious agent. Positron emission tomography–computed tomography (PET-CT) revealed increased metabolic activity around the implanted stent. During a subsequent percutaneous transluminal angioplasty, blood was sampled directly from the affected fistula segment after dilatation, and 16S ribosomal RNA gene polymerase chain reaction (PCR) with amplicon NGS demonstrated the presence of Neoehrlichia mikurensis. Antimicrobial therapy with rifampicin was initiated for 6 weeks. Clinical and laboratory indicators of infection normalized, and follow-up PET-CT demonstrated resolution of the previously increased metabolic activity. Neoehrlichiosis is an emerging tick-borne disease prevalent in Eurasia. Clinical manifestations of neoehrlichiosis include fever, myalgia, arthralgia, thrombotic events, and cutaneous lesions; and are most frequently observed in immunocompromised individuals. Because this intracellular bacterium is detectable only through molecular methods, the infection is likely underrecognized. Our case demonstrates that neoehrlichiosis should be considered in immunosuppressed patients presenting with fever and vascular access complications. A high index of clinical suspicion is required, because untargeted NGS from peripheral blood may fail to detect the pathogen, whereas local sampling can increase the likelihood of diagnosis.