Latent tuberculosis infection in a subject with diabetes mellitus - A case report

Abstract

Introduction: Patients suffering from diabetes mellitus type 1 often have impaired cell-mediated immunity and are prone to infectious diseases. The aim of this paper is to present a case study on latent tuberculosis infection (LTBI) in a 46 year-old female health care worker (a nurse at the department for tuberculosis in young children) who has been having type 1 diabetes for 20 years. Materials and methods: Tuberculin skin test was performed using 2 tuberculin units (Tuberkulin RT-23, Statens Serum Institute, Copenhagen, Denmark). Blood for interferon gamma (IFN-γ) release assay, (IGRA) was sampled intest tubes containing specific-antigens of mycobacterium tuberculosis (ESA T-6, CFP10 and TB7.7). After incubation (22 hours) at 37°C, IFN-γ concentration in plasma was determined by ELISA assay (QuantiFERON-TB Gold In Tube - Cellestis Ltd., Victoria, Australia). For positive control, blood was sampled by mitogene phytohemagglutinin and for negative control by heparin. Results: Tuberculin skin test was negative (induration 6 mm) and test result of IFN-γ release from activated lymphocytes (≥ 0.35 kIU/L) positive. Normal cellular immunity was confirmed by positive control sample. The subject showed no signs of active tuberculosis. Conclusion: In a nurse suffering from type 1 diabetes who has worked for years with tuberculosis patients, LTBI was detected by IFN-γ release assay rather than by tuberculin skin test. In spite of the long lasting diabetes, reaction of IFN-γ release toward specific tuberculosis antigens has been preserved and active tuberculosis has not developed.