Leprosy is a treatable chronic infectious disease, caused by Mycobacterium leprae, not highly transmittable that affects mainly the skin and peripheral nerves. Often neglected because it is rare in western countries, it may be encountered in patients coming back from endemic areas. Diagnostic criteria include underpigmented patches with loss of sensation, thickened peripheral nerves and acid-fast bacilli on skin smears or biopsy material. The variation of the cellular immune response determines the different forms of the disease (tuberculoid to lepromatous) and the neurological impairment. A precise diagnosis is mandatory to adjust the treatment. Among the neurological complications the leprosy reactions are the most important because they may result in increased nerve damage and compromised recovery if the specific treatment is delayed.