Written by Choo, Pharmacist

What is Leprosy?

Leprosy, also known as Henson disease, is a chronic infectious disease that is caused by a slow-growing type of gram-positive bacteria called Mycobacterium leprae (M. leprae).

It primarily affects the peripheral nerves, skin, upper respiratory tract, eyes, and nasal mucosa. Thus, leprosy may lead to severe, disfiguring skin sores and nerve damage in the arms, legs, and skin areas around the body.

Mycobacterium leprae is a rod-shaped obligate intracellular bacterium (only grows inside of certain human and animal cells). The bacteria grow very well in the body’s macrophages (a type of immune system cell) and Schwann cells (cells that cover and protect nerve axons). It attacks the nerves of the affected areas. If left untreated, the nerve damage can result in paralysis of hands and feet. In very advanced cases, the person may have multiple injuries due to lack of sensation and eventually resulting in the apparent loss of toes and fingers. Corneal ulcers and blindness can also occur if facial nerves are affected. Other signs of advanced Hansen’s disease may include loss of eyebrows and saddle-nose deformities resulted from damage to the nasal septum.

Image result for leprosy worldwide

Around the world, as many as 2 million people are permanently disabled as a result of Hansen’s disease. Country where the disease is widespread includes:

  • Africa: Democratic Republic of Congo, Ethiopia, Madagascar, Mozambique, Nigeria, United Republic of Tanzania
  • Asia: Bangladesh, India, Indonesia, Myanmar, Nepal, Philippines, Sri Lanka
  • Americas: Brazil


Symptoms on the affected skin

  • Discoloured patches of skin.
  • Thick, stiff or nodules on the skin
  • Painless ulcers on the soles of feet
  • Painless swelling or lumps on the face or earlobes
  • Loss of eyebrows or eyelashes

Symptoms on the affected nerve

  • Numbness of affected areas of the skin
  • Muscle weakness or paralysis
  • Eye problems that may lead to blindness

Symptoms of advanced leprosy

  • Paralysis and crippling of hands and feet
  • Shortening of toes and fingers due to reabsorption
  • Chronic non-healing ulcers on the bottoms of the feet
  • Blindness and loss of eyebrows
  • Nose disfigurement


Although human-to-human transmission is the primary source of infection. However, chimpanzees, mangabey monkeys and armadillos may carry and transfer M. leprae to humans.


Diagnosis and classification

Confirm diagnosis can be done by taking a sample of the affected skin or nerve (biopsy) to look for the bacteria under the microscope. The modified Ziehl-Neelsen stain is an example of the special staining techniques used to view the acid-fast organisms under the microscope. The skin biopsy usually reveals perivascular inflammation of the papillary dermis with lymphohistiocytic inflammation.

WHO classify leprosy with clinical criteria based on number of skin lesions and nerve involved:

  • Paucibacillary leprosy: 4 to 5 skin lesions
  • Multibacillary leprosy: > 5 skin lesions

Besides, WHO also classify leprosy with skin smear if facility available

  • 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



Leprosy disease is treated with a combination of antibiotics. Typically, 2 or 3 antibiotics are used at the same time. These are dapsone with rifampicin, and clofazimine is added for some types of the disease. Multidrug therapy helps prevent the development of antibiotic resistance by the bacteria, which may otherwise occur due to length of the treatment. Treatment usually lasts between one to two years. The illness can be cured if treatment is completed as prescribed.

Antibiotics used during the treatment will kill the bacteria that cause leprosy. But while the treatment can cure the disease and prevent it from getting worse, it does not reverse nerve damage or physical disfiguration that may have occurred before the diagnosis. Thus, it is very important that the disease be diagnosed as early as possible, before any permanent nerve damage occurs.

  • Multibacillary leprosy: Multidrug therapy with dapsone, rifampicin, and clofazimine
  • Paucibacillary leprosy: Modified multidrug therapy with dapsone and rifampicin



Prevent contact with droplets from nasal and other secretions from patients with untreated M. leprae infection. In addition, treatment of patients with appropriate antibiotics stops the person from spreading the disease.



  1. Cdc.gov. (2020). References | Hansen’s Disease (Leprosy) | CDC. [online] Available from: https://www.cdc.gov/leprosy/resources/index.html [Accessed 9 Jan. 2020].
  2. Hartzell, J., Zapor, M., Peng, S. and Straight, T. (2004). Leprosy: A Case Series and Review. Southern Medical Journal, 97(12), pp.1252-1256.
  3. C., S., K.C., G., Gyawali, P., Singh, M. and Sijapati, M. (2019). Leprosy – eliminated and forgotten: a case report. Journal of Medical Case Reports, 13(1).
  4. Scollard, D., Adams, L., Gillis, T., Krahenbuhl, J., Truman, R. and Williams, D. (2006). The Continuing Challenges of Leprosy. Clinical Microbiology Reviews, 19(2), pp.338-381.
  5. World Health Organization. (2020). WHO Multidrug therapy (MDT). [online] Available from: https://www.who.int/lep/mdt/en/ [Accessed 8 Jan. 2020].
  6. Worobec, S. (2012). Current approaches and future directions in the treatment of leprosy. Research and Reports in Tropical Medicine, p.79.