[Plant thorn synovitis in a child].

The first Danish case report of a thorn-induced arthritis is presented. The symptoms and histopathology are similar to those in the cases described in foreign literature. The clinical presentation is that of transient acute synovitis, followed by an asymptomatic period, and later by a period of persistent symptoms, often after the thorn injury was forgotten. Histopathology shows granulomatous synovitis. Synovectomy and removal of the plant thorn usually results in normal joint function. The diagnosis should be remembered in undiagnosed cases of monoarticular arthritis.