[Rickettsia conorii: a new cause of erythema nodosum].

A case of 26 year old male with an infection caused by Rickettsia conorii (RC) associated to erythema nodosum (EN) is presented. The patient had EN together with a high temperature and toxic symptoms 2 weeks after camping in the mountains. The diagnosis was made by ascertaining IgM titers positive to RC by indirect immunofluorescence (IIF). The disease disappeared 24 hours after the initiation of treatment with doxiciclin. Based on this observation, we consider RC to be an etiologic agent which should be taken into account in the differential diagnosis of EN.