CD40LG and scrub typhus: Nevertheless, based on the diagnostic criteria in South Korea, tsutsugamushi disease can be confirmed when the antibody titer rises more than 4 times between that measured in the acute phase and that in the convalescent serum, or when the IgM antibody titer is 1:16 or higher, or when the IgG antibody is 1:256 or higher in a single serological test.[8,14,18] Tsutsugamushi disease could not be differentiated in this case at admission because the patient came to the hospital with an unusually large eschar for more than 2 weeks after the first eschar occurred.