RESUMEN
BACKGROUND: Type 1 leprosy reaction, also known as "reversal reaction", is related to cellular immune responses to Mycobacterium leprae antigens. The risk factors that trigger type 1 leprosy reactions are poorly understood. Leprosy with concurrent tetanus is rare, and there are no publicly available reports of a leprosy patient infected with tetanus that induced type 1 leprosy reactions. CASE PRESENTATION: A 56-year-old Chinese Han female presented to our hospital with symptoms of erythematous plaques and pain over her left upper limb for 2 days and foreign object sensation in her throat for 3 days. The patient had a 6-year history of leprosy. Type 1 leprosy reactions were initially considered, followed by treatment with methylprednisolone. Two days later, the patient's symptoms were aggravated, with neck muscle tension and difficulty in opening her mouth, and the erythematous plaques had spread over most of her left upper limb. After further careful examinations, we confirmed the diagnosis of tetanus with concurrent type 1 leprosy reactions. The patient was given anti-tetanus treatment for 12 days and anti-leprosy reaction treatment for 4 months; the diseases were eventually controlled. CONCLUSIONS: This report suggests that tetanus infection may be a trigger for type 1 leprosy reactions.