[Incidence and type of monoclonal or biclonal gammopathies in scrub typhus]

Korea is an endemic area of scrub typhus and it is a common seasonal febrile illness. Although, various humoral immune responses to scrub typhus have been documented, no association between gammopathy and scrub typhus has ever been reported. We analyzed the incidences and types of monoclonal and biclonal gammopathies in scrub typhus for better coping with those gammopathies in scrub typhus.

Anti-Orientia tsutsugamushi antibody-positive sera identified by indirect immunofluorescence assay were acquired from 40 patients with confirmed scrub typhus. Monoclonal and biclonal gammopathies were screened by protein electrophoresis and were confirmed using immunofixation electrophoresis (IFE). Laboratory findings on admission of the patients with monoclonal or biclonal gammopathy were investigated retrospectively to characterize the gammopathies.

Monoclonal or biclonal gammopathies were detected in 30% (12/40) of patients with scrub typhus (IgG-lambda, 40%; IgG-kappa, 30%; IgM-kappa, 10%; IgM-lambda, 10%; IgA-kappa, 5%; IgA-lambda, 5%). Concentrations of clonal immunoglobulin were less than 3 g/dL in all gammopathies, and hypercalcemia was not detected in any of the patients.

Our results suggest possible association between gammopathies and scrub typhus. Further studies in larger series will be needed for exact incidence and clinical course of gammopathies in scrub typhus.