Abstract: This paper report a 25-year-old female patient with erythema and ulceration of lower extremities for 3 years, papules and nodules of back for 6 months. In the past 3 years, she was diagnosed and treated in other hospital for many times, all of which were diagnosed and treated according to "allergic vasculitis" with poor results. The patient was diagnosed as lepromatous leprosy (LL) by skin tissue fluid and pathological examination. Because the patient tested positive for HLA-B13:01, it was not appropriate to take dapsone orally. Rifampicin(600mg/m), moxifloxacin (400mg/d), and chlorphenphenazine(300mg/m, 50mg/d) were given treatment, while methylprednisolone was used to prevent facial neuritis. During treatment, type Ⅱ leprosy reaction occurred, and symptoms were relieved after the addition of thalidomide. At present, the follow-up is still in progress, and the skin lesions have subsided significantly. This case suggests that we still need to further strengthen the training of medical personnel, early detection of leprosy patients, reduce the rate of missed diagnosis and misdiagnosis.Electrophysiological examination, leprae nucleic acid detection, serological tests, MBT(multiplex biomarker test) kits, etc., may have great potential in early identification of leprosy patients and reduce diagnostic delay.

Key words: Lepra lepromatosa, Allergic vasculitis, Misdiagnosis