What Is Leprosy? Symptoms, Causes, Diagnosis, Treatment, and Prevention

For centuries, leprosy was considered a highly contagious and dangerous disease that only struck — and deformed — those who were unlucky enough to be cursed. (1) In fact, biblical leprosy (tzaraat) not only refers to a skin condition, but also “the state of ritual impurity” and punishment for sins. The real meaning of leprosy was simply lost in translation somewhere along the way. (2) Even today, the term “leper” is widely used to mean an outcast, and that’s highly offensive to the hundreds of thousands of people affected by the disease today. (3)

Despite the lingering mystery and stigma, the medical community now understands that leprosy, also known as Hansen’s disease, is a chronic and progressive infectious disease caused by a slow-to-grow bacterium called Mycobacterium leprae (M. leprae). (3)

This bacterium invades the skin, eyes, nasal lining, and peripheral nerves (nerves outside the brain and spinal cord). (3) And while leprosy is, in fact, contagious, it’s not nearly as transmissible as was thought in ancient times, which means that isolating those infected is never warranted. (1,4)

Unfortunately, there are usually no immediate leprosy symptoms to clue you in that you’ve become infected by M. leprae. Instead, it can take at least a year to develop symptoms, with most people showing signs of leprosy only five to seven years after contracting the disease. (5)

In general, leprosy affects the skin (in the form of rashes, lesions, and bumps) and the peripheral nerves. Numbness on skin spots, loss of feeling in the hands and feet, and muscle weakness are all symptoms of peripheral nerve loss. Leprosy symptoms vary depending on how far the disease has progressed. In some of the worst cases, where leprosy hasn’t been treated in a timely manner, disfigurement and blindness can occur. (4) Some symptoms of leprosy include:

• Spots on the Skin These usually appear on the arms, legs, or back. They may be darker or lighter than normal skin, or slightly red. (3) They don’t burn or hurt, but they may become raised, and nodules may form. (1)
• Painless Swelling This occurs on the face and earlobes. (6)
• Eye Issues Light sensitivity can be an early symptom. (7) And if the disease has invaded facial nerves, the blinking reflex can be lost, which can lead to dry eyes, ulcers, and even blindness. (3)
• Hair Loss The skin spots may lose hair, and eyebrows or eyelashes may fall out. (3,6)
• Numbness and Tingling Skin spots feel numb, and a loss of sensation can occur, first in a finger or toe, then progressing to hands and feet. Tingling can occur, too. (7)
• Foot Ulcers Painless ulcers may appear on the soles of the feet. (6)
• Dry, Cracked Skin If leprosy has damaged the nerves in the skin, this can cause sweat and oil glands to stop functioning, leading to dry and cracked skin on the hands and feet. (1)
• Curled Fingers Over time, the small muscles in the hands can become paralyzed, and fingers and thumbs can curl. (3)
• Muscle Weakness This can be experienced in the hands and feet. (6)
• Injury to Extremities Loss of feeling can increase chances of injury due to burns, cuts, and destructive pressure on hands and feet. (1)
• Facial Deformities If the disease is left untreated, bacteria can enter the mucous lining of the nose, leading to internal scarring that may cause the nose to collapse. (3)
• Sexual Dysfunction Men with more severe leprosy may have erectile dysfunction and become infertile. (8)

M. leprae is the slow-growing bacterium behind leprosy. If a person’s immune response to the bacterium is weak — or does not occur at all — M. leprae can spread through the skin, the peripheral nerves, and, at times, into deeper tissues. (4) Fortunately, more than 95 percent of people around the world are naturally immune to M. leprae, making leprosy a rare disease. (8) Those who are more at risk for contracting leprosy include:

• People Living in High-Risk Areas In 2018, 71 percent of leprosy cases were in Southeast Asia. The Americas and Africa represented 15 and 10 percent of new cases, respectively. Meanwhile, the countries with the most new cases were India, Indonesia, and Brazil. In 2017, 14 countries reported at least 1,000 new cases of leprosy, including Brazil, India, Indonesia, Bangladesh, Democratic Republic of Congo, Madagascar, Myanmar, Philippines, Mozambique, Ethiopia, Nepal, Nigeria, Sri Lanka, and Tanzania. (9)
• Gene Susceptibility It’s thought that those who contract leprosy have genes that make them susceptible to the infection once exposed. (8) Susceptibility to leprosy tends to run in families, but the inheritance pattern is still unknown. (4)
• Ethnicity Individuals of Asian and Pacific Islander descent have elevated odds of contracting multibacillary leprosy (see more on this below). Right now, the reason is unknown. (10)
• Children They are more susceptible to developing leprosy than adults. (11) But in the United States, the occurrence of leprosy in children is still rare. (12)
• Individuals With Weakened Immune Systems People with chronic diseases like diabetes, HIV, or heart disease may be more likely to develop leprosy. (5)
• Contact With an Armadillo This may sound odd, but individuals who’ve either handled the animal or simply spent time outdoors in an area where armadillos live are at an elevated risk. (7) Armadillos carrying the bacteria have been found mostly in the Southern United States, including Arkansas, Alabama, Louisiana, Mississippi, Texas, and Florida. Scientists estimate that more than 100,000 armadillos carry the bacteria here. (13)

If you suspect that you may have leprosy and you are in the United States, know that your dermatologist or general practitioner may not have leprosy top-of-mind during the examination process, since the disease is so rare in this country. Physicians in the United States are likely unfamiliar with leprosy symptoms. (8) To diagnose leprosy, healthcare workers look for at least one of these fundamental signs:

• At least one discolored (pale or reddish) and numb patch of skin.
• One or more thickened or enlarged peripheral nerves with loss of sensation.
• Positive skin smear results. Here, a modest incision is made in the affected skin, and a sample is extracted. The sample is then examined for the presence of the bacterium. (1,15,16)

Next, to confirm a diagnosis of leprosy, a skin or nerve biopsy is performed. For the skin biopsy, a sample is taken from the edges of skin patches to be further examined under a microscope. And for the nerve biopsy, a small piece of material is extracted from a thickened peripheral nerve to be more closely examined. (16)

While some serological tests (blood tests that look for antibodies) have been developed to detect leprosy, right now they’re not sensitive enough to be relied upon for diagnosis. (16)

Leprosy occurs on a continuum: Some cases are mild, affecting a few areas of skin, while others are more severe, affecting many skin areas and causing damage to nerves and organs that can lead to disfigurement. While some physicians and researchers use a more complex system to define and categorize various forms of leprosy, most use the following two-pronged, more simplified classification. (5)

Paucibacillary Leprosy (PB) This classification, which includes indeterminate, tuberculoid, and borderline tuberculoid leprosy, is based on a negative skin smear, meaning patients have relatively few bacteria in the skin and nerves. With PB leprosy, individuals most likely have five or fewer affected skin areas, although sometimes there are more. (8)

Multibacillary Leprosy (MB) Individuals in this category have a large number of bacteria present in their skin and nerves, and their symptoms are more widespread. Those with MB leprosy tend to have six or more affected skin areas. Patients may experience thickening of the peripheral nerves and organs, such as the eyes, nose, and testicles; bones may also be involved. Multibacillary leprosy encompasses mid-borderline, borderline lepromatous, and lepromatous leprosy. (1,5,8)

Prognosis of Leprosy

With oral antibiotics and prompt treatment, leprosy is curable. In fact, most individuals diagnosed with leprosy in the United States have little or no disability upon diagnosis. In addition, the majority of people with leprosy are able to carry on with normal activities during treatment with little interruption. (17)

If recent nerve damage is present at diagnosis, prompt treatment may be able to improve the damage or stave off further issues. Unfortunately, if nerve damage occurred years prior to diagnosis, recovery isn’t possible and disabilities become permanent. (17)

If significant nerve damage occurs, a long-term management plan involving a variety of healthcare professionals, such as physicians, an occupational therapist, physical therapist, ophthalmologist, and podiatrist, can help prevent disability. Some ways this can be achieved include:

• Splints to immobilize and protect specific nerves from harm
• Contoured eye mask at night to protect eyes from dryness
• Prescribed footwear and orthotics to shield feet from injury and ulceration
• Tendon release procedure, such as toe flexor release, to help relieve pressure
• Education on how to compensate for lack of pain sensation, such as frequent extremity inspection and protective equipment (17)

Once treatment begins, it usually takes one to two years to be completely rid of the disease. That said, nerve damage or physical disfiguration that occurs as a result of leprosy cannot be reversed. (18)

Leprosy is a highly treatable — and even curable — disease, especially when diagnosed early before any permanent nerve damage has occurred. (8) Here’s how leprosy should be treated, according to the World Health Organization’s latest guidelines from 2018.

Leprosy should be combated with a combination of three drugs, consisting of rifampin (Rifadin), dapsone (Aczone), and clofazimine (Lamprene). (15) This plan of action, called multidrug therapy (MDT), is prescribed in order to prevent antibiotic resistance. After just a few doses — which are generally given at home — individuals become noninfectious. (1,3)

Treatment for paucibacillary leprosy should last six months; treatment for multibacillary leprosy should extend to 12 months. For those who are resistant to the above meds, alternatives like clarithromycin (Biaxin), minocycline (Minocin), or a quinolone may be used — and treatment may take longer. (15) Unlike in the past, when quarantine was a given, today individuals with leprosy do not require isolation. (1)

Side effects of MDT are generally mild and temporary — and serious side effects are rare. These side effects may include darkening of the skin, dry skin, or scaliness and are best treated with acetaminophen (Tylenol), ibuprofen (Advil), or corticosteroids. (19)

Prevention of Leprosy

It’s still not entirely known how leprosy is transmitted, but it’s widely believed that it’s spread through the respiratory tract. This means that people can contract leprosy by inhaling droplets expelled through the coughing or sneezing of an infected person. (8) Even then, roughly half of those with leprosy likely contracted the disease not through a rogue sneeze or cough, but through close, extended contact with an infected individual. (8) Transmission of the disease from mother to child during pregnancy has been reported. (9)

It’s also possible to contract leprosy through contact with an infected armadillo. Some of these animals, which are found in the southern United States, are naturally infected with the bacteria that cause leprosy. While the risk of getting leprosy from an infected armadillo is extremely low, it’s still advisable to avoid contact of any kind with these animals.

Leprosy is not spread via sexual intercourse or casual contact, such as shaking hands or sitting next to an individual with the disease. (20)

As many as half of all those with leprosy have reactions to multidrug therapy; these reactions can include pain and swelling in the skin and nerves, fever, muscle aches, and pain and redness in the eyes. (3) These types of reactions, however, do not mean that the disease is worsening or that the medications aren’t working. Instead, they’re a sign that multidrug therapy is succeeding: These symptoms are the body’s reaction to the now dead M. leprae lingering in the system. (It can take years for the body to completely rid itself of all the dead bacteria.)

Some people experience these reactions before multidrug therapy has even started. In those cases, the body is reacting to bacteria that its own immune system has killed. Reaction may occur on and off for a period of time, and reactions can differ depending on the type of leprosy. (1) For instance:

• Those with paucibacillary leprosy may experience type 1 reactions or reversal reactions that involve swelling or reddening of preexisting lesions. (21)
• Those with multibacillary leprosy may experience type 2 reactions or erythema nodosum leprosum (ENL), (21) which is characterized by fever; raised, red, painful skin nodules; and possible nerve pain and tenderness. (Joint issues, eye inflammation, and inflammation of the testicles may also occur.) (1)
• People of Mexican ancestry may experience something called Lucio’s phenomenon. This is a rare reaction involving difficult-to-heal ulcers, and it affects those with multibacillary leprosy. (21)

Whether the reactions are experienced before or after MDT, it’s important to treat them quickly, as they increase one’s chances of nerve damage to the eyes, hands, and feet. Some reactions can be quelled with over-the-counter medicines, such as aspirin (Vazalore) or acetaminophen, while others require a prescription for prednisone (Deltasone) or thalidomide (Thalomid). (1)

Finally, it’s possible for leprosy relapse to occur 20 years after MDT: 0.8 percent of multibacillary patients and between 0.6 and 3 percent of paucibacillary patients experience relapse. Having a high bacterial load before starting treatment, experiencing a large number of lesions, and inadequate or irregular therapy increases the risk of relapse. (9)

Roughly 250,000 new cases of leprosy are diagnosed every year, with between 100 and 250 occurring in the United States. (4)

Of new U.S. cases, 72 percent were reported in Arkansas, California, Florida, Hawaii, Louisiana, New York, and Texas. (23)

The largest proportion of people with cases of leprosy in the United States identified as Asian or South Pacific Islander.  (23)

Leprosy has been reported among individuals from every state. (17)

Since the 1990s, roughly 175 new leprosy cases are reported annually in the United States. (17)

Compared with folks living in other nations, individuals residing in Asian and Pacific Island countries have a higher chance of contracting multibacillary leprosy. Right now, the reason for this remains unclear, but it’s been speculated that, perhaps, factors like genetics, comorbidities, micronutrient deficiencies, or a limited gene pool within an island nation may be contributing factors. (10)

Not much is known about the relationship between specific ethnic groups in the United States and their risk of leprosy. But it has been noted that individuals living in the States who are of Micronesian and Marshallese descent are also at an elevated risk of MB. Leprosy is more prevalent in Southeast Asian immigrants living in Toronto, as well. Still, there’s currently no research to show why this ethnic group is more susceptible to MB. (10)

As discussed above, if left untreated, leprosy can lead to a number of other conditions, such as neuropathy, blindness, erectile dysfunction, hair loss, and muscle weakness.