Clinical course of monoclonal and oligoclonal gammopathies in patients infected with Orientia tsutsugamushi.

Although we have encountered many cases of monoclonal gammopathies (MGs) or oligoclonal gammopathies (OGs) in patients with Orientia tsutsugamushi infections, the clinical course of MG/OG associated with these infections has rarely been reported. We serially monitored 18 cases of MG/OG that appeared in the acute phase or early convalescent phase of scrub typhus. All MGs/OGs associated with infection with O. tsutsugamushi disappeared 7-15 weeks after treatment with doxycycline. In three cases of scrub typhus, MGs/OGs appeared before seropositive conversion (presence of antibodies against O. tsutsugamushi) and disappeared before seronegative conversion. Understanding our cases may be helpful for relevant clinical counseling and making appropriate medical decisions to avoid unnecessary invasive or cost-intensive diagnostic procedures for MGs/OGs in scrub typhus, especially in disease-endemic areas. We also suggest that 2-4 months after antibiotic treatment might be the optimal follow-up time to observe the disappearance of MGs/OGs associated with O. tsutsugamushi infections.