Leprosy: Definition, Symptoms and Diagnosis

Leprosy also known as Hansen disease, is a chronic infectious disease of humans caused by the bacteria Mycobacterium leprae. It was so named after the scientist, Armauer Hansen from Norway who discovered the bacteria mycobacterium leprae (M. leprae) as the cause of leprosy in 1873.

It affects the skin and the nerves of the hands and feet, as well as the eyes and the lining of the nose. In some cases, leprosy can also affect other organs, such as the kidneys and testicles in men. If left untreated, leprosy can cause deformities of the hands and feet, blindness, and kidney failure.

This disease is classified by the number and type of skin sores you have. Specific symptoms and treatment depend on the type of leprosy you have. The types are:


  • Indeterminate leprosy: refers to a very early form of leprosy that consists of a single skin lesion with slightly diminished sensation to touch. It will usually progress to one of the major types of leprosy.
  • Tuberculoid leprosy: A mild, less severe form of leprosy. People with this type have only one or a few patches of flat, pale-colored skin (paucibacillary leprosy). The affected area of skin may feel numb because of nerve damage underneath. Tuberculoid leprosy is less contagious than 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 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.
  • 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: A more severe form of the disease. It has widespread skin bumps and rashes (multibacillary leprosy), numbness, and muscle weakness. The nose, kidneys, and male reproductive organs may also be affected. It is more contagious than tuberculoid leprosy.



Symptoms of Leprosy

The disease progresses very slowly. Most people who have leprosy do not develop symptoms for at least a year after being infected by the bacteria. In most cases, it takes 5 to 7 years for symptoms to develop. Leprosy damages the nerves and muscles. It may cause sores, lesions, lumps, and bumps to appear on the skin.

Depending on the type, symptoms may include:

  • Skin sores or lesions that do not heal after several months (lesions are flat or slightly elevated and light in color or slightly red).
  • Skin lumps and bumps that can be disfiguring.
  • Numbness of the skin because of damage to the nerves under the skin.
  • Muscle weakness.
  • Pain (joints).
  • Deep pressure sensations are decreased or lost.
  • Nerve injury.
  • Weight loss.
  • Blisters and or rashes.
  • Ulcers, relatively painless.
  • Skin lesions of hypopigmented macules (flat, pale areas of skin that lost color).
  • Eye damage (dryness, reduced blinking).
  • Hair loss (for example, loss of eyebrows).
  • Facial disfigurement (for example, loss of nose).
  • Erythema nodosum leprosum: tender skin nodules accompanied by other symptoms like fever, joint pain, neuritis, and edema.




Leprosy is relatively rare today, but it is prevalent in some countries of Asia, Africa, and South America. Worldwide, there are about 700,000 new cases reported each year, with about 800,000 cases under treatment in 1998.

There are an additional estimated two to three million persons who have residual deformities and disabilities from the disease, even though they have been cured of the infection. Some of the countries with the largest number of cases are India, Brazil, Indonesia, Bangladesh, Myanmar, Nigeria, and Mozambique.

The way in which the disease is transmitted is not fully understood. The bacteria grow only in living hosts and have not been grown in laboratory media, except in certain kinds of mice, rats, and armadillos. Some wild armadillos also carry the bacteria.

Most likely way of spread appears to be through the respiratory tract, since large numbers of bacteria are sometimes found in the noses and mouths of untreated patients.

When these are released into the environment, they can be inhaled by other susceptible persons. Most people have a natural immunity to the disease and will not contract it even if they are exposed to it. Only about 5 percent of all people are susceptible to the disease. More than one-half of new cases give no history of any known contact with a infected persons.




How Leprosy is Diagnosed and Treated

Your doctor will ask you questions about your medical history and the symptoms you are experiencing. He or she will probably want to remove a tiny piece of the affected skin (called a biopsy) to check for the Mycobacterium leprae (M. leprae) bacteria.

Leprosy can be cured. In the last two decades, 16 million people with leprosy have been cured. The World Health Organization (WHO) provides free treatment for all people with leprosy.

Treatment depends on the type of leprosy that you have and antibiotics are used to treat the infection. Long-term treatment with two or more antibiotics is recommended, usually from six months to a year. People with severe leprosy may need to take antibiotics longer. Antibiotics cannot treat the nerve damage.

Anti-inflammatory drugs are used to control nerve pain and damage related to leprosy. This may include steroids, such as prednisone.

Patients with leprosy may also be given thalidomide, a potent medication that suppresses the body’s immune system. It helps treat leprosy skin nodules. Thalidomide is known to cause severe, life-threatening birth defects and should never be taken by women who are pregnant or women who may become pregnant.





Without treatment, leprosy can permanently damage your skin, nerves, arms, legs, feet, and eyes. Complications of leprosy can include:

  • Blindness or glaucoma.
  • Disfiguration of the face (including permanent swelling, bumps, and lumps).
  • Erectile dysfunction and infertility in men.
  • Kidney failure.
  • Muscle weakness that leads to claw-like hands or an inability to flex the feet.
  • Permanent damage to the inside of the nose, which can lead to nosebleeds and a chronic, stuffy nose.
  • Permanent damage to the nerves outside the brain and spinal cord, including those in the arms, legs, and feet. Nerve damage can lead to a dangerous loss of feeling. A person with leprosy-related nerve damage may not feel pain when the hands, legs, or feet are cut, burned, or otherwise injured.






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