Leprosy: Classifications, Prognosis & Treatment

Hands of a patient with leprosy

Leprosy is a chronic infection caused by the bacteria Mycobacterium leprae.  Pale patches on the skin are usually the first sign of the disease, they are painless and do not itch, so are often ignored by the patient. In the past, nerve damage and other complications occurred as the disease progressed. Leprosy can lead to disfiguring skin sores and nerve damage in the arms and legs. However, leprosy is actually not that contagious. You can catch it only if you come into close and repeated contact with nose and mouth droplets from someone with untreated leprosy. Children are more likely to get leprosy than adults. Leprosy is also known as Hansen’s disease, after the scientist who discovered M. leprae in 1873.

Classifications of Leprosy

Two classification systems exist in the medical literature: the WHO system and the Ridley-Jopling system

The Ridley-Jopling system is composed of six forms or classifications, listed below according to increasing severity of symptoms:

  • Indeterminate leprosy: a few hypopigmented macules; can heal spontaneously, this form persists or advances to other forms
  • Tuberculoid leprosy: a few hypopigmented macules, some are large and some become anesthetic (lose pain sensation); some neural involvement in which nerves become enlarged; spontaneous resolution in a few years, persists or advances to other forms
  • Borderline tuberculoid leprosy: lesions like tuberculoid leprosy but smaller and more numerous with less nerve enlargement; this form may persist, revert to tuberculoid leprosy, or advance to other forms
  • Mid-borderline leprosy: many reddish plaques that are asymmetrically distributed, moderately anesthetic, with regional adenopathy (swollen lymph nodes); the form may persist, regress to another form, or progress
  • Borderline lepromatous leprosy: many skin lesions with macules (flat lesions) papules (raised bumps), plaques, and nodules, sometimes with or without anesthesia; the form may persist, regress or progress to lepromatous leprosy
  • Lepromatous leprosy: Early lesions are pale macules (flat areas) that are diffuse and symmetric; later many M. leprae organisms can be found in them. Alopecia (hair loss) occurs; often patients have no eyebrows or eyelashes. As the disease progresses, nerve involvement leads to anesthetic areas and limb weakness; progression leads to aseptic necrosis (tissue death from lack of blood to area), lepromas (skin nodules), and disfigurement of many areas, including the face. The lepromatous form does not regress to the other less severe forms. Histoid leprosy is a clinical variant of lepromatous leprosy that presents with clusters of histiocytes (a type of cell involved in the inflammatory response) and a grenz zone (an area of collagen separating the lesion from normal tissue) seen in microscopic tissue sections.

The Ridley-Jopling classification is used globally in evaluating patients in clinical studies. However, the WHO classification system is more widely used; it has only two forms or classifications of leprosy. 

The 2009 WHO classifications are simply based on the number of skin lesions as follows:

  • Paucibacillary leprosy: skin lesions with no bacilli (M. leprae) seen in a skin smear
  • Multibacillary leprosy: skin lesions with bacilli (M. leprae) seen in a skin smear

However, the WHO further modifies these two classifications with clinical criteria because “of the non-availability or non-dependability of the skin-smear services. The clinical system of classification for the purpose of treatment includes the use of number of skin lesions and nerves involved as the basis for grouping leprosy patients into multibacillary (MB) and paucibacillary (PB) leprosy.” Investigators state that up to about four to five skin lesions constitutes paucibacillary leprosy, while about five or more constitutes multibacillary leprosy.


Leprosy is caused by the bacterium Mycobacterium leprae. It is not very contagious and it has a long incubation period (time before symptoms appear), which makes it hard to know where or when someone caught the disease. Children are more likely than adults to get the disease.

Leprosy has two common forms: tuberculoid and lepromatous. Both forms produce sores on the skin. However, the lepromatous form is most severe. It causes large lumps and bumps (nodules).

Effective medications exist. Isolating people with this disease in “leper colonies” is not needed.


Unfortunately, the early signs and symptoms of leprosy are very subtle and occur slowly, usually over years. The symptoms are similar to those that may occur with syphilis, tetanus, and leptospirosis. Numbness and loss of temperature sensation are some of the first symptoms that patients experience. As the disease progresses, the sensations of touch, then pain, and eventually deep pressure are decreased or lost. Signs that occur, such as relatively painless ulcers, skin lesions of hypopigmented macules (flat, pale areas of skin), and eye damage like dryness, reduced blinking are experienced before the large ulcerations, loss of digits, and facial disfigurement develop. This long-term developing sequence of events begins and continues on the cooler areas of the body (for example, hands, feet, face, and knees).

Exams and Tests

Lepromin skin test can be used to tell the two different forms of leprosy apart, but it is not used to diagnose the disease

  • Skin lesion biopsy
  • Skin scraping examination


An effective cure for leprosy has been available since 1982 in the form of multidrug therapy a combination of three drugs taken daily for six to 12 months. But while treatment halts the progression of this cruel disease, it cannot turn the clock back in terms of disability. A clawed hand or foot drop can be restored with surgery. Surgery, however, cannot restore the feeling to hands and feet meaning they can become easily injured. Protective footwear can be worn to reduce the chances of injury and of ulcers developing. The blinking mechanism can also be restored to the eye by surgery. But once eyesight has been lost as a result of injury to the eye, nothing can be done to reverse the situation.


Diagnosing the disease early is important. Early treatment limits damage, prevents a person from spreading the disease, and allows the person to have a normal lifestyle.