Leprosy is an infectious disease that causes severe, disfiguring skin sores and nerve damage in the arms, legs, and skin areas around your body. Leprosy has been around since ancient times. Outbreaks have affected people on every continent.

But leprosy, also known as Hanson’s disease, isn’t 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.

Today, about 208,000 people worldwide are infected with leprosy, according to the World Health Organization, most of them in Africa and Asia. About 100 people are diagnosed with leprosy in the U.S. every year, mostly in the South, California, Hawaii, and some U.S. territories.

Leprosy Symptoms

Leprosy primarily affects your skin and nerves outside your brain and spinal cord, called the peripheral nerves. It may also strike your eyes and the thin tissue lining the inside of your nose.

The main symptom of leprosy is disfiguring skin sores, lumps, or bumps that don’t go away after several weeks or months. The skin sores are pale-colored.

Nerve damage can lead to:

  • Loss of feeling in the arms and legs
  • Muscle weakness

It usually takes about 3 to 5 years for symptoms to appear after coming into contact with the bacteria that causes leprosy. Some people do not develop symptoms until 20 years later. The time between contact with the bacteria and the appearance of symptoms is called the incubation period. Leprosy's long incubation period makes it very difficult for doctors to determine when and where a person with leprosy got infected.

What Causes Leprosy?

Leprosy is caused by a slow-growing type of bacteria called Mycobacterium leprae (M. leprae). Leprosy is also known as Hansen's disease, after the scientist who discovered M. leprae in 1873.

It isn’t clear exactly how leprosy is transmitted. When a person with leprosy coughs or sneezes, they may spread droplets containing the M. leprae bacteria that another person breathes in. Close physical contact with an infected person is necessary to transmit leprosy. It isn’t spread by casual contact with an infected person, like shaking hands, hugging, or sitting next to them on a bus or at a table during a meal.

Pregnant mothers with leprosy can’t pass it to their unborn babies. It’s not transmitted by sexual contact either.

Forms of Leprosy

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

  • Tuberculoid. 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.
  • Lepromatous. A more severe form of the disease. It brings 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.
  • Borderline. People with this type of leprosy have symptoms of both the tuberculoid and lepromatous forms.

You may also hear doctors use this simpler classification:

  • Single lesion paucibacillary (SLPB): One lesion
  • Paucibacillary (PB): Two to five lesions
  • Multibacillary (MB): Six or more lesions

Leprosy Diagnosis

If you have a skin sore that might be leprosy, the doctor will remove a small sample of it and send it to a lab to be examined. This is called a skin biopsy. Your doctor may also do a skin smear test. If you have paucibacillary leprosy, there won’t be any bacteria in the test results. If you have multibacillary leprosy, there will be.

You may need a lepromin skin test to see which type of leprosy you have. For this test, the doctor will inject a small amount of inactive leprosy-causing bacteria just underneath the skin of your forearm. They’ll check the spot where you got the shot 3 days later, and then again 28 days later, to see if you have a reaction. If you do have a reaction, you may have tuberculoid or borderline tuberculoid leprosy. People who don’t have leprosy or who have lepromatous leprosy won’t have a reaction to this test.

Leprosy Treatment

Leprosy can be cured. In the last 2 decades, 16 million people with leprosy have been cured. The World Health Organization provides free treatment for all people with leprosy. 

Treatment depends on the type of leprosy that you have. Antibiotics are used to treat the infection. Doctors recommend long-term treatment, usually for 6 months to a year. If you have severe leprosy, you may need to take antibiotics longer. Antibiotics can’t treat the nerve damage that comes with leprosy.

Multidrug therapy (MDT) is a common treatment for leprosy that combines antibiotics. That means you’ll take two or more medications, often antibiotics:

  • Paucibacillary leprosy: You’ll take two antibiotics, such as dapsone each day and rifampicin once a month.
  • Multibacillary leprosy: You’ll take a daily dose of the antibiotic clofazimine in addition to the daily dapsone and monthly rifampicin. You’ll take multidrug therapy for 1-2 years, and then you’ll be cured.

You may also take anti-inflammatory drugs to control nerve pain and damage related to leprosy. This could include steroids, like prednisone.

Doctors sometimes treat leprosy with thalidomide, a potent medication that suppresses your immune system. It helps treat leprosy skin nodules. Thalidomide is also known to cause severe, life-threatening birth defects. Never take it if you’re pregnant or plan to become pregnant.

Leprosy Complications

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

Complications of leprosy can include:

  • Blindness or glaucoma
  • Iritis
  • Hair loss
  • Infertility
  • 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 a not being able to flex your feet
  • Permanent damage to the inside of your nose, which can lead to nosebleeds and a chronic stuffy nose
  • Permanent damage to the nerves outside your brain and spinal cord, including those in the arms, legs, and feet

Nerve damage can lead to a dangerous loss of feeling. If you have leprosy-related nerve damage, you may not feel pain when you get cuts, burns, or other injuries on your hands, legs, or feet.