Long-term persistence of IgG- and IgM-antibodies against leptospira after mild leptospirosis has not been reported. In a 45-year-old female pet-shop worker with carpal tunnel syndrome, accompanied by arthralgias, coughing, repeatedly elevated temperature, followed by easy fatigability, personality change, memory and speech disturbance, blurred vision, myalgia and swollen lymph nodes, leptospirosis was diagnosed, based upon history, clinical findings, and serological investigations. After the described symptoms had disappeared following doxycyclin for 2 weeks, IgG- and IgM-antibodies against leptospira remained positive during the next three years. This case illustrates that leptospirosis may start as carpal tunnel syndrome and that the severity of leptospirosis does not seem to be related to the intensity of the humoral immune response against the causative agent.