In the year 1953, the VI. International Leprosy Congress in Madrid dealt with the classification of different forms of leprosy for the first time. The classification of the various symptoms of leprosy was carried out with regard to clinical, bacteriological, immunological and histopathological criteria. A distinction was drawn between:

  • tuberculoid,
  • lepromatous,
  • borderline and
  • intermittent leprosy.

In 1964, Ridley und Jopling introduced different categories of leprosy for research and scientific work. The tuberculoid form of leprosy was then referred to as TT Form and the lepromatous form as LL-Form, both as stable and polar. The borderline form of the disease was considered as instable, since it can change towards the TT-Form, or, as occurs more often, towards the LL-Form.

At present, Leprosy is only divided into two groups for practical reasons in the fieldwork and the control of epidemics:

  • Paucibacillary Leprosy PB (low quantity of bacteria) and
  • Multibacillary Leprosy MB (high quantity of bacteria)
Distinction of the above mentioned forms of Leprosy within the current classification:
  • Paucibacillary Leprosy Form PB contains the early stage of Leprosy (Lepra indeterminata LI), the Tuberculoid form of Leprosy as well as the Borderline Leprosy BT.
  • Multibacillary Leprosy MB contains the lepromatous form LL, Borderline Leprosy BB and BL.