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Leprosy : Classification

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Leprosy can be classified on the basis of clinical manifestations, skin smear results, and findings on skin biopsy.

Ridley-Jopling Classification of Leprosy (Hansen's Disease): It is based on the clinical presentation and host immune response. This classification is the one most frequently used in the U.S. The disease is subclassified into:

  • Indeterminate (I)
  • Tuberculoid (TT)
  • Borderline Tuberculoid (BT)
  • Borderline (BB)
  • Borderline Lepromatous (BL)
  • Lepromatous (LL)

  • WHO Classification of Leprosy: The WHO classification of leprosy has been widely adopted all over the world. It consists of 3 categories: paucibacillary single lesion leprosy, paucibacillary leprosy, and multibacillary leprosy. Skin smears were initially used to distinguish between paucibacillary (negative skin smear; no evidence of advanced disease on biopsy) and multibacillary leprosy (positive skin smears; biopsy indicating advanced disease). However, the skin smears are difficult to perform, lack reliability, and are not always available. For practical purposes, the disease is classified into the three categories based on the number of skin lesions and nerves involved:
    • Paucibacillary single lesion leprosy (one skin lesion)
    • Paucibacillary leprosy (2-5 skin lesions)
    • Multibacillary leprosy (6 or more skin lesions)
    Generally, paucibacillary disease is equivalent to I, TT, and BT disease in the Ridley-Jopling Classification, and multibacillary disease is equivalent to BB, BL, and LL disease.

    Case History: The image shows biopsy-proven skin lesions of lepromatous leprosy. The patient was a 56 y/o male with a prolonged history of generalised erythema, photosensitivity and widely disseminated reddish brown infiltrated papulonodules and plaques. Image courtesy of: Shahbaz Janjua, MD; Global Skin Atlas; Used with permission.

    World Health Organization - Leprosy

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