Image Taken from WHO



Leprosy also known as Hansen’s disease is an infectious disease caused by slow growing acid fast bacilli called Mycobacterium leprae. It is an obligate intracellular bacterium. The bacilli have affinity for the cooler tissues. It can affect the nerves, skin, eyes, and lining of the nose (nasal mucosa). Mycobacterium leprae invades either dermal nerves or main peripheral nerves trunks situated superficially, in regions that are relatively cooler like face and limbs.

Global situation

  • According to official reports received from 138 countries from all WHO regions, the global registered prevalence of leprosy at the end of 2015 was 176 176 cases (0.18 cases per 10 000 people).
  • In 2015, the number of new cases reported globally was 211 973 (0.21 new cases per 10 000 people).
  • In 2014 the number of new cases reported was 213 899, and in 2013 the number of new cases reported was 215 656.
  • The number of new cases indicates the degree of continued transmission of infection. Global statistics show that 203 600 (96%) of new leprosy cases were reported from 22 priority countries.
  • Over the past 20 years, more than 16 million leprosy patients have been treated.
  • The prevalence rate of the disease has dropped by 99%: from 21.1 cases per 10 000 people in 1983 to 0.2 cases per 10 000 people in 2015.
  • A dramatic decrease has been achieved in the global disease burden: from 5.2 million people with leprosy in 1985, to 805 000 people in 1995, 753 000 in 1999 and 176 176 people with leprosy at the end of 2015.


  • It is not known exactly how leprosy spreads between people.
  • Prolonged, close contact with someone with untreated leprosy over many months is needed to catch the disease.

Individuals cannot get leprosy from:

  • Shaking hands or hugging with the patient
  • Sitting next to the patient on the bus
  • Sitting together at a meal
  • It is also not passed on from a mother to her unborn baby during pregnancy
  • It is also not spread through sexual contact with the patient.

Signs and Symptoms

Some symptoms seen on skin are:

  • Growths (nodules) on the skin.
  • Discolored patches of skin, usually flat, that may be numb and look faded which is lighter than the skin around.
  • Thick, stiff or dry skin
  • Painless ulcers on the soles of feet
  • Painless swelling or lumps on the face or earlobes
  • Loss of eyebrows or eyelashes

Symptoms caused by damage to the nerves are:

  • Numbness of affected areas of the skin
  • Muscle weakness or paralysis (Particularly in hands and feet)
  • Enlarged nerves (especially those around knee and elbow)
  • Eye problems that may lead to blindness

Symptoms caused by disease in mucous membrane are:

  • A stuffy nose
  • Nosebleeds

If Leprosy is not treated on time there can be some signs like:

  • 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
  • Loss of eyebrows
  • Nose disfigurement


  • Leprosy can be recognized by appearance of patches of skin that may look lighter or darker that the normal skin.
  • Doctor needs to take a sample of the skin or nerve (skin/nerve biopsy) to look for the bacteria under the microscope, to confirm the diagnosis.



  • Onset of leprosy is insidious. Bacilli enter the body through respiratory system.
  • After entering the body, bacilli migrate towards the neural tissue and enter the Schwann cells.
  • It can also be found in, macrophages, muscle cells and endothelial cells of blood vessels.
  • Bacilli then multiply slowly within these cells, get liberated from the destroyed cells and then enter other unaffected cells.
  • Specific and effective cell mediated immunity (CMI) can provide protection to a person against leprosy.
  • When specific CMI is effective in eliminating/ controlling the infection, lesions heal spontaneously or it produces pauci-bacillary (PB) type of leprosy. If CMI is poor; the disease spreads uncontrolled and produces multi-bacillary (MB) type of leprosy.


Pathogenesis of Leprosy


  • Multi drug therapy (MDT) is used for the treatment of leprosy
  • The combination of antibiotics used in MDT is dapsone, rifampicin and clofazimine.
  • The Multi drug therapy strategy 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.






  1. WHO
  2. CDC
  3. NLEP