Leprosy is a bacterial infection that grows very slowly and can have severe health consequences if treatment is not received. It attacks the nervous system, causing significant disfigurement.

With modern drug-based interventions, leprosy is entirely curable. The World Health Organization (WHO) and other groups are focused on eradicating the disease.

In 2015, the official global number of people with leprosy was registered as just over 176,176, down from 5.2 million in the 1980s. All presentations of the disease are considered chronic.

This article will explain what leprosy is, as well as the symptoms, diagnosis, and treatment of the condition.

Fast facts on leprosy

  • A bacterial infection causes leprosy.
  • The primary symptoms of leprosy are lesions on the skin and a lack of sensation in the nervous system.
  • The bacteria that causes leprosy are Mycobacterium leprae and Mycobacterium lepromatosis.
  • Leprosy can now be successfully treated using multi-drug therapy.

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Leprosy attacks cells in the immune and nervous systems. This can cause physical effects on the limbs and senses.

Leprosy, also known as Hansen's disease, is a bacterial infection caused by Mycobacterium leprae (M. leprae) or Mycobacterium lepromatosis (M. lepromatosis).

Severely affected individuals are thought to transmit the bacteria by droplets from the mouth or nose, though this is not well defined.

However, despite its reputation, leprosy is not particularly contagious. Around 95 percent of the world's population is naturally immune and, even after prolonged exposure, will not pick up the disease.

The bacteria responsible for leprosy preferentially attack macrophages, a key part of the immune system, and the Schwann cells that support cells for the nervous system.

M. leprae and lepromatosis multiply slowly. Leprosy has been eliminated in most countries, which is defined as a prevalence rate of less than one case per 10,000. However, in some countries, leprosy is able to transmit to other people before it is detected, making it difficult to control the spread of the disease effectively.

The symptoms of leprosy can present differently in different people with the condition.

The main symptoms include:

  • the appearance of skin lesions that are lighter than normal skin and remain for weeks or months
  • patches of skin with decreased sensation, such as touch, pain, and heat
  • muscle weakness
  • numbness in the hands, feet, legs, and arms, known as "glove and stocking anesthesia"
  • eye problems
  • enlarged nerves, especially in the elbows or knees
  • stuffy nose and nosebleeds
  • curling of the fingers and thumb, caused by paralysis of small muscles in the hand
  • ulcers on the soles of the feet.

Injuries, breaks, and burns can go unnoticed, due to the numbing of sensation caused by nerve damage, potentially becoming infected or more seriously injured. Over time, the extremities can be lost to repeated damage.

The wounds are also more likely to become infected, as immune defenses are weakened by leprosy. The reabsorption of cartilage by the body means that these secondary infections can result in tissue loss. This leads to the characteristic shortening of the toes and fingers seen in leprosy.

Damage to the mucous membrane that coats the inside of the nose can sometimes lead to internal damage and scarring. The nose might eventually collapse.

Leprosy can destroy the nerves responsible for blinking. This can lead to the eyes becoming dried out and prone to infection, potentially resulting in ulceration and blindness.

There are a number of approaches to classifying leprosy.

Some simply split the disease into two groups, tuberculoid and lepromatous, with most types of leprosy being some mix of the two. Both types produce lesions on the skin, but the lepromatous form is more severe and causes the additional formation of large lumps and bumps.

The largest risk factor for contracting leprosy is contact with another person who is infected with M. leprae or M. lepromatosis. Malnutrition may also play a part in leprosy risk.

Individuals who are immunosuppressed could be more at risk of developing leprosy. However, for unknown reasons, this increased risk does not apply to individuals with HIV.

People with both HIV and leprosy can however find that their condition worsens when they begin antiviral treatment.

Certain families seem to be more prone to leprosy than others, suggesting that some individuals may have a genetic susceptibility to leprosy. Research suggests that a defect in cell-mediated immunity could lead to a likelihood of contracting leprosy.

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The National Jalma Institute for Leprosy in India is a treatment center dedicated to resolving leprosy.

Treatment for leprosy consists of a multi-drug therapy approach that lasts between 6 and 12 months.

The first drug found to be effective, dapsone, has been in use since 1946. Later, some resistance to the drug was identified, and others were developed for use in cases where the disease was resistant. These drugs were rifampicin and clofazimine.

Today, all three drugs can be given in combination, depending on the severity of illness. This kills the M. leprae and M. lepromatosis bacteria and cures the patient.

The side effects of leprosy treatment are rare but can include:

  • Dapsone can lead to minor anemia
  • Rifampicin can trigger abnormal liver test results that clear up after the drug is stopped. It may also produce a harmless orange coloration of the sweat, urine, or tears.
  • Clofazimine might cause a slight darkening of the skin that returns to normal once treatment has stopped.

A physician usually bases the diagnosis of leprosy on the visual recognition of the signs and symptoms. Laboratory tests are only necessary in rare cases.

In the countries where leprosy is most common, the presence of just one of the following symptoms is enough to make a diagnosis:

  • skin lesions consistent with leprosy and sensory loss, with or without thickened nerves
  • positive skin smears

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Leprosy is a misunderstood disease that causes homelessness, poverty, and isolation.

Leprosy is not particularly contagious, and once treatment has been underway for 2 to 4 weeks, the individual is no longer contagious at all. Despite this fact, so-called "leper colonies" still operate in India, China, and some African countries.

There is no medical reason for leprosy patients to be removed from society.

In these countries, the significant social stigma around leprosy makes life with the condition isolated and difficult.

Although organizations such as WHO are working tirelessly to reduce and eventually eradicate leprosy, the issue of stigma for sufferers of leprosy is proving harder to remove.

Individuals bearing the scars of leprosy can earn significantly less money, chances of marriage can be significantly reduced, mothers with the disease may stop breastfeeding their babies, and affected children can be shunned from their homes and villages permanently.

The emotional stress and anxiety of leprosy can cause mental health problems, leading to further isolation and sometimes the cessation of treatment. Unemployment is common, and begging is often the only option left, adding to stress, marginalization, and feelings of worthlessness.

Because of the fear of this stigma, people who have contracted leprosy sometimes hide their symptoms and do not seek help or treatment. This allows the condition to worsen and increases the risk of complications. It also increases the chances of transmission to others in the community.

The ideal ways to prevent the spread of leprosy are the early diagnosis and treatment of the condition in people to whom the disease has been transmitted.

However, due to poor medical infrastructure and the stigmas attached to leprosy, education, and provisions in various communities around the world are not enough to completely eradicate leprosy.

The following steps can be taken to promote the prevention of leprosy:

  • providing education and self-care support
  • monitoring the condition and its symptoms on an on-going basis and referring severe cases
  • managing day-to-day injuries and disabilities that develop
  • educate locals about injury prevention and wound cleaning

Important progress has been made so far, but scientific and humanitarian education programs must continue to work in unison to minimize and eventually remove leprosy from the human experience.