What Is Leprosy?

Leprosy, known as Hansen's Disease, is a disease from ancient times that still exists today. It affects the skin, peripheral nerves, and mucosal membranes. Across the world, there were more than 202,000 new cases in 2019, according to the World Health Organization (WHO). More than 16 million people have been cured of this disabling, disfiguring disease since treatments became available in the 1980s.

The first breakthrough came in 1873, when Dr. Armauer Hansen of Norway found it was caused by the Mycobacterium leprae bacteria. By the 1940s, there was a drug to treat leprosy, and by the 1960s there were two more. Today, all three are used together to treat leprosy in people.

Leprosy also occurs in animals, like armadillo, and is considered a zoonotic disease in the United States. That means it can be transmitted from animals to people.

This article explains the causes and symptoms of leprosy. More important is that it will help you to understand that leprosy can be cured, and why it is so critical to seek and complete treatment.

Leprosy Symptoms

The earliest sign of leprosy is commonly a spot on the skin that may be slightly redder, darker, or lighter than the person's normal skin. But because leprosy has impacts other than skin, the symptoms differ depending on what body parts are affected. For skin, people may also see:

• Small growths on the skin
• Thick, stiff, or dry skin
• Painless sores on the soles of feet
• Swelling or lumps on the face and ears
• Loss of eyebrow or eyelash hair

If left untreated, leprosy can cause serious nerve damage. This usually begins as a sense of numbness in spots where nerves are involved. Leprosy may then progress to cause:

• Paralysis in the hands or feet
• Potential amputation of the hands or feet
• Permanent curling or total loss of toes or fingers
• Loss of vision if nerves around the eyes are infected
• nosebleeds and damage to the nose, which may collapse

Causes

Just six states accounted for 69% of all U.S. leprosy cases in 2020, including Louisiana, where the national treatment facility is located. Experts there say about 95% of people have a natural immunity to the disease. Leprosy also is not very contagious.

But when it is, leprosy is spread through the air through droplets when someone with an untreated case coughs or sneezes. This close contact is important, and it's one reason why more recent WHO guidelines call for people who are around an infected person, like friends or family members, to also be treated.

According to the National Hansen’s Disease Program, a potential route through animal contact also is a growing cause for concern. A 2011 international study by researchers from France, Venezuela, and the U.S. made the first genetic connection between leprosy in people and animals. Another study in 2015 confirmed leprosy in both the armadillo and humans in the southeastern U.S.

Additional studies since then have found zoonotic leprosy in other countries, and in other animals including monkeys. This supports concern over animal-human transmission.

Diagnosis

Leprosy is diagnosed by taking a skin sample (biopsy) and examining it under the microscope to look for leprosy bacteria.

Another test used for diagnosis is a skin smear. A small cut is made in the skin and a small amount of tissue fluid is taken. This also is put under a microscope to confirm the presence of leprosy bacteria.

Treatment

The good news is that leprosy is curable. In 1981, WHO recommended the use of MDT, a combination of three antibiotics—usually dapsone, rifampicin, and clofazimine—for treatment. This treatment may take six months to a year.

In 2018, WHO continued the multidrug approach but also added a single dose approach using rifampicin for leprosy prevention in family, friends, and other social contacts of a confirmed case. WHO has made the drugs free since 1995.

During the course of treatment, the body may react to the dead bacteria with pain and swelling in the skin and nerves. This is treated with medication. In 2020, WHO also issued guidelines for treating the recurring inflammation that happens in about 50% of cases.

Prognosis

Before treatment was available, a diagnosis of leprosy meant suffering and pain and being shunned by society. Today, antibiotics and good skin care will prevent the disease from destroying the body. Perhaps in the future, a vaccine will eliminate it altogether.

Summary

Leprosy is an ancient disease with a historic stigma attached. Yet it's also a modern disease, with thousands of cases each year—including some in the developed world. What may seem like a rash can develop into a serious bacterial infection that affects vision, and may cause paralysis or the loss of feet and hands should it progress.

Fortunately, people respond well to treatment where it is available. The risk may be low in the U.S., but knowing the symptoms of leprosy and how it is treated may be the best way to protect yourself and those around you.

A Word From Verywell

Many people in the United States have heard of leprosy but think it's a condition that is seen only in the developing world. That's not true, and 159 cases happened in the U.S. in 2020. There's no reason to be overly vigilant because it's still quite rare. What it does mean is that leprosy may seem obvious in another country but get missed in the U.S. If you have reason to think it's leprosy, insist that your health worker check for that.