Lyme arthritis in a 12-year-old patient after a latency period of 5 years

Lyme arthritis (LA) may be confused with other rheumatic diseases, particul arly in the absence of a history of erythema migrans (EM). We report the ca se of a 12-year-old patient who developed a large effusion of the right kne e joint,The titer for antinuclear antibodies was 1:80 and the test for rheu matoid factor was negative. Investigations for antibody response to Borreli a burgdorferi demonstrated remarkable elevation of IgG antibody and no spec ific IgM response. These results were confirmed by immunoblotting reactivit y with the bands p83/100, p58, p43, p41, p39, OspA, p30, OspC, p21, and p17 . We subsequently learned that the child had suffered a tick bite followed by an EM 5 years earlier and had been treated with trimethoprim/sulfamethox azole at that time. The patient now was given intravenous ceftriaxone, 2 g daily for 14 days. In the absence of clinical improvement 3 weeks later a k nee joint aspiration was performed which resulted in a positive polymerase chain reaction (PCR) test for B. burgdorferi DNA (OspA) in the synovial flu id. The patient fully recovered 2 months later without further treatment. T he case indicates that the latency period between EM and onset of LA may la st up to 5 years. In addition to serologic test methods, analysis of synovi al fluid using PCR may be decisive for making the final diagnosis of LA.