[Clinical diagnosis of Lyme borreliosis in case of joint and muscular presentations].

The diagnosis of Lyme borreliosis in case of joint and muscular presentations is generally suggested by epidemiological factors. However, as a rule, laboratory testing is required to confirm the diagnosis. When considering the epidemiology of Lyme borreliosis in France, the only areas free of ticks infected by Borrelia burgdorgeri sl, are those close to the Mediterranean sea or at high altitude. The risk is greatest in the Alsace region. Exposure is particularly high among forest workers and people who use the countryside for their leisure activities. The likelihood of infection following a tick bite is difficult to assess; indeed, the bite site may remain unnoticed. A medical history of erythema migrans, if untreated, is a major diagnostic clue, although the association appears to be less consistent in France than in the US. Lyme arthritis generally arises apparently spontaneously. It is characteristically mono- or oligo-articular, asymmetrical, predominantly affects the knee, and has an intermittent course. Synovial cysts and enthesitis are common. Myositis is rare, polymorphic, and has been linked to other symptoms in the same localizations. Minor arthralgia and myalgia frequently occur, principally early in the course of the infection. It was suggested that sequels of the disease include so-called fibromyalgic syndromes. The principal differential diagnosis as far as arthritis is concerned, is made on spondylarthropathy and chronic juvenile arthritis. Rheumatoid arthritis is another pathology, although Lyme arthritis does sometimes evolve to chronicity.