The objective of this study was to confirm the role of B. miyamotoi in the etiology of ITBB-WOEM in Udmurtia and to investigate in detail the clinical presentation of this "new" disease. 50 adult patients with ITBB-WOEM treated in Republic Hospital for Infectious Diseases, Udmurtia, in 2010-2011 had PCR-confirmed infection by B. miyamotoi. The laboratory evidence of co-infection by other pathogens, including tick-borne encephalitis virus, B. burgdorferi sensu lato, A. phagocytophilum, E. chaffeensis, and E. muris, were absent. All patients had a tick bite from 10 to 18 days before the acute disease onset. The main clinical signs were high fever, fatigue, headache, chill, and sweat. Clinical, biochemical, and instrumental investigations also showed the signs of functional impairment of various organs: the liver (in about half of the patients), kidney (in 10 patients), heart (6 patients), etc. In contrast, acute ITBB with erythema migrans was usually a localized infection without a pronounced intoxication syndrome and impairments of the organs. ITBB-WOEM caused by B. miyamotoi is a systemic disease that is clinically closer to relapsing fevers transmitted by argasid ticks than to Lyme borreliosis. The number of B. miyamotoi infections in Russia may be comparable with that of Lyme disease cases, so the investigations of epidemiology, clinical presentation and therapy of this "new" disease are urgently requested.