Abstract: A 62-year-old male presented with erythematous slightly squamous plaques and nodules on the right lower limb for more than 10 years, ulcers for 1 year. The patient had been misdiagnosed as sacroicosis and received mutiple immunosuppressive therapies without satisfactory result. At last, we made use of polymerase chain reaction and detected Mycobacterium tuberculosis complex DNA from skin biopsy tissue. The diagnosis of cutaneous tuberculosis was made and anti-tuberculosis treatment was effective.

Key words: cutaneous tuberculosis, immunosuppressive therapy, polymerase chain reaction, sarcoidosis