Arthritis in Mediterranean spotted fever. An immune complex mediated synovitis.

Arthromyalgia are frequent in Mediterranean spotted fever (MSF) (16-76%) but arthritis is rare. We report on a 54-year-old woman who, 1 day after suffering from fever, headache and malaise, developed a painful and swollen left knee. A maculopapular rash and the characteristic 'tache noire' skin lesion appeared 5 days later. Immune complexes were detected in serum and in the SF and normalized following improvement of clinic manifestations. These findings along with a low C3 complement level in the SF suggest that arthritis was mediated by immune complex deposits.