Leprosy, also known as Hansen's disease or Hansenitis, is an infectious disease known from antiquity, and historically carrying a great social stigma. It is now understood to be quite difficult to transmit, and can be managed and often cured with drugs available in developed countries, and increasingly worldwide.
The principal manifestations are dermatologic and periperhal neuropathy, but it can progress to systemic disease.
It appears to have originated in India circa 700 BCE, moved to the Far East around 400 BCE, and to Europe in the fourth century CE, peaking in the fourteenth century. It spread from Europe to the Americas.
The pathogen had long been believed to be Mycobacterium leprae, but, in 2009, it was discovered that some cases are caused by the closely related Mycobacterium lepromatosis. The latter species causes the diffuse form of lepromatous leprosy found in Mexico and the Caribbean. 
Diagnosis, especially in the early stages, can be challenging because the signs and symptoms are subtle. Usually first manifesting as a skin disease, it produces hyposensitive areas. While there are few reasons to recommend cigarette smoking, patients often first sought medical attention when they smelled burning flesh, but felt no pain, when a cigarette, held between fingers, burned to a stub.
- Paucibacillary disease: continued for 6 months,
- Multibacillary disease: treatment for one year with:
- Dapsone at 100 mg/d
- rifampin at 600 mg once a month
- clofazimine at 300 mg once a month and 50 mg/d for 1 year
- Single skin lesion: single treatment with:
- Han XY, Sizer KC, Thompson EJ, Kabanja J, Li J, Hu P, et al. (Oct 2009), "Comparative sequence analysis of Mycobacterium leprae and the new leprosy-causing Mycobacterium lepromatosis.", J Bacteriol 191 (19): 6067-74