Pattern of joint involvement in children with Lyme arthritis.

Following the clinical observation of a peculiar joint pattern in children with Lyme arthritis, we classified the pattern of joint involvement in children with oligoarticular arthritis (2-4 joints) of different causes, including Lyme arthritis, juvenile chronic arthritis and juvenile spondyloarthropathy, as: (1) symmetrical: arthritis of the same joints on both sides of the body; (2) unilateral: all involved joints on the same side; (3) predominantly unilateral: joints involved on the contralateral side also showed ipsilateral involvement; (4) oblique: involvement on the contralateral side of one or more joints that did not show ipsilateral involvement. The oblique pattern was found in 13 of 42 children with early-onset pauciarticular juvenile chronic arthritis and in 17 of 32 patients with juvenile spondyloarthropathy, but not in 32 of 32 children with Lyme arthritis. If confirmed, these results may have implications for the diagnosis and pathogenesis of Lyme arthritis.