An unusual case of chronic relapsing tetanus associated with mandibular osteomyelitis.

A 55-year-old man underwent radiation therapy due to malignant lymphoma of the neck. Eight years after the therapy he developed tetanus. It appears that the radiation therapy resulted in mandibular necrosis, and that this lesion may have been the infectious focus of tetanus. Treatment with penicillin G was very effective in the acute stage, and chronic administration of metronidazole prevented relapse of the disease. However in spite of injections of tetanus toxoid, symptoms of tetanus returned when the administration of metronidazole was discontinued because the infectious focus could not be completely removed. This is the first report of chronic relapsing tetanus associated with radiation-induced mandibular osteomyelitis, and demonstrates that tetanus can occur due to mandibular focus but the chronic administration of metronidazole can prevent relapse.