Leprosy (Hansen's disease) is a chronic infectious disease that affects the skin and peripheral nerves. Although restricted to major endemic countries, it is the most common cause of peripheral neuropathy worldwide (Pfaltzgraff 1993; Sabin 1993). The disease is caused by Mycobacterium leprae, which has a predilection for Schwann cells. Since the introduction of an effective treatment based upon multidrug therapy (dapsone, clofazimine, and rifampin) and recommended by the World Health Organization (WHO), the prevalence of leprosy has dramatically decreased (World Health Organization 2000). However, the disease is still a public health problem in many countries, with an estimated global prevalence of nearly 600,000 cases as of the end of 2001 (World Health Organization 2002). Damage to peripheral nerves is a key component of leprosy and, together with typical skin lesions, accounts for the major traditional clinical features of the disease. Little is known about the mechanism by which the mycobacteria infect Schwann cells, but recently some evidence has emerged. A glycoprotein (alpha-dystroglycan) that binds to the surface of M. leprae also binds to a molecule on the surface of the Schwann cell and provides a potential mechanism for internalization of the bacilli (Rambukkana 1997; Freedman 1999). In addition, it is clear that the most profoundly affected sites have distinctive common features, such as being superficial, with a low ambient temperature, and located along potentially constricting anatomical structures such as nerve sheaths.
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