A Case of Loxoscelism in Southern France

An 80-year-old man living in Fréjus in southern France had a cellulitis on the right arm (Figure 1). The patient had no fever, chills, systemic symptoms, or other clinical signs. He felt a slight pain in his arm during the night and while folding his arm, he crushed a spider. The spider’s body was immediately recovered and then identified by an entomologist (Figure 2). This typical skin lesion and the spider identification defined this spider bite as an envenomation by a Loxosceles sp. spider. The outcome was good after only antalgic treatment. Infections with herpes zoster virus, herpes simplex virus, and Panton-Valentine toxin-positive Staphylococcus aureus can be misdiagnosed as necrotic arachnidism. Nevertheless, the characteristic red, white, and blue sign visible for the first few days (Figure 1) has been associated with loxoscelism. This sign is a consequence of erythema, ischemia, and thrombosis observed from the periphery to the center of the lesion. Loxosceles rufescens was suspected because it is endemic to Mediterranean regions (L. reclusa is not endemic to this region).