Last updated:
3/18/2025
Years published: 1986, 1990, 1992, 1993, 1997, 1998, 1999, 2007, 2009, 2025
NORD gratefully acknowledges Gioconda Alyea, MD (FMG), MS, National Organization for Rare Disorders, for assistance in the preparation of this report.
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Summary
Leprosy, also known as Hansen’s disease, is a chronic infectious disease caused by the bacteria Mycobacterium leprae. It primarily affects the skin, peripheral nerves, mucosa of the upper respiratory tract and the eyes. If left untreated, it can lead to progressive and permanent disabilities including nerve damage, muscle weakness and deformities.1
People with leprosy may also experience stigma and discrimination which can impact their social and emotional well-being. However, leprosy is curable, and early treatment can prevent complications and stop transmission.
Leprosy is not highly contagious. It spreads through droplets from the nose and mouth of an untreated person during close and frequent contact over a long period.
However, leprosy does not spread through casual interactions such as:1
Once treatment begins the patient is no longer contagious.1,2
Leprosy primarily affects the skin and nerves. Common symptoms include:1,5
In over 90% of patients, the first symptom noticed is numbness. Sensory loss progresses in stages; temperature sensation is lost first, and loss of light touch follows, and pain and deep pressure are lost last .5
Nerve damage may appear years before skin lesions develop. The peripheral nerves are affected very early during leprosy, as evidenced by the decrease or absence of sensation in the earliest skin lesions. Most commonly, neuropathy manifests with loss of sensory perception, though in some people it can present with acute pain (acute neuritis) or chronic pain (neuropathic pain) later in the course of the disease
The first skin changes often appear as a single or a few pale (hypopigmented) patches, which may evolve into different forms of leprosy.
If left untreated, leprosy can cause severe nerve damage leading to paralysis, deformities and disabilities.
Leprosy has 2 classification schemas: the 5-category Ridley-Jopling system and the simpler 3 category, WHO standard.4,5,6,7,8
Ridley-Jopling system classification
Leprosy classified using the Ridley-Jopling system is based on skin symptoms, nerve involvement, biopsy findings and the number of bacteria present. This classification helps determine how the immune system responds to the disease. It includes five types included in two main categories, paucibacillary and multibacillary.
There is also an indeterminate form. This classification of the disease typically changes as it evolves during its progression or management. The Ridley-Jopling system is used globally and forms the basis of clinical studies of leprosy. It also may be more useful in guiding treatment regimens and assessing risk for acute complications. The classification is as follows:4
Paucibacillary leprosy (fewer bacteria present)
Multibacillary leprosy (more bacteria present)
This classification helps doctors choose the best treatment based on the type and severity of the disease.
Lepra reactions (occurs in 30%–50% of affected people) are sudden immune system responses that can worsen symptoms before or after starting treatment. These reactions are the leading cause of nerve damage, disability, and deformity in leprosy. There are two main types:6
Acid-fast bacilli are a group of bacteria (that include M. leprae and M. lipomatosis) that share the characteristics of acid fastness. Acid fastness is a physical property that gives a bacterium the ability to resist decolorization by acids during staining procedures. This means that once the bacterium is stained, it cannot be decolorized using acids routinely used in the process. This important and unique feature of certain bacteria makes it possible to classify and detect them using relatively easy laboratory procedures such as microscopy.9
WHO classification
The WHO classification of leprosy is based on the number of bacteria present and the immune response of the person. It can range from a mild, localized form to a severe, widespread form.3,4,5,6,7,8
Paucibacillary (PB) or tuberculoid leprosy: This type has a lower bacterial load. It is characterized by a few (1–2) sharply defined red patches with raised borders or a single large lighter (hypopigmented) patch of skin (less than 10 cm), dry, rough, hairless skin in the patches due to loss of sweating with complete loss of sensation in affected areas. Affected nerves are thickened and tender.
Borderline tuberculoid leprosy (BT): This type is similar to tuberculoid leprosy, but with larger lesions (5–20 in number), less well-defined borders, asymmetrical distribution and satellite lesions (small patches surrounding a larger one). The loss of sensation is less pronounced than in TT and the nerve involvement can cause deformities and disabilities
Multibacillary (MB) lepromatous leprosy: This type has a higher bacterial load and is the most severe form. Early symptoms include nasal congestion, discharge and bleeding. There is also swelling and thickening of the limbs, especially ankles and legs, with ulcers as well as many lighter (hypopigmented) and reddish patches of skin, with a shiny surface and normal sensation in early stages. It progresses to small, solid bumps (nodules) and larger, flat, raised areas (plaques) appearing all over the body. People also have a leonine facies – thickening of the forehead, loss of eyebrows and eyelashes (madarosis), distortion of the nose and thickened earlobes. It may lead to severe complications affecting multiple organs:
Clinical variants of lepromatous leprosy include:3,4,5,6,7,8
There is also a form known as pure neural leprosy (PNL) seen mainly in India and Nepal. There are no skin lesions, only peripheral nerve damage, leading to tender, thickened nerves and numbness. It can result in trophic ulcers (painless wounds due to numbness). Diagnosis requires a nerve biopsy.
Leprosy is caused by slow-growing bacteria called Mycobacterium leprae and Mycobacterium lepromatosis.1,2
The disease likely spreads when an untreated person coughs or sneezes, releasing droplets that contain the bacteria. A healthy person may become infected if they breathe in these droplets.
Most people (about 95%) cannot get infected because their immune system fights off the bacteria naturally.
To catch the disease there must be prolonged, close contact with someone with untreated leprosy for many months. Leprosy is not spread through sexual contact and cannot be passed from mother to baby during pregnancy.2
In the southern United States, some armadillos are naturally infected with the bacteria that cause leprosy. While there is a small chance that the bacteria can spread from armadillos to humans, the risk is very low, and most people who come into contact with armadillos do not get the disease.
Leprosy is NOT spread through casual contact, such as hugging, shaking hands, or sitting next to someone on a bus, sharing meals or drinks or touching objects like doorknobs, clothing, or books. Once a person starts treatment, they can no longer spread the disease to others.2
Some people are more vulnerable to leprosy due to inherited differences in their immune response.3
The immune response to M. leprae has two parts: innate immunity (determined by genetics) and acquired immunity (developed in response to infection).3
Innate immunity (genetic protection) helps some people resist infection. Certain genes, like PARK2/PACRG and NOD2 affect susceptibility to leprosy.4
Acquired immunity determines how the body reacts to M. leprae after exposure. The severity of the disease depends on the person’s ability to mount a strong immune response which is influenced by non-HLA (human leukocyte antigen) genes.4
Some ethnic groups and families may have a higher risk due to genetic factors.
People with impaired cell-mediated immunity (a type of immune response important for fighting infections) are more likely to develop leprosy. HIV infection, malnutrition and immunosuppressive treatments (such as medications used after organ transplants or for autoimmune diseases) can increase susceptibility.3
Children and adolescents are at greater risk, possibly due to weaker immune defenses and higher exposure to infectious contacts. Males are more frequently affected than females, though the reasons for this are not fully understood.3
While exposure to M. leprae is necessary to develop leprosy, most people (about 95%) are naturally resistant and do not get sick.3
Leprosy is rare in the United States. Most cases in the U.S. occur in people who were infected in countries where the disease is more common.1,2
Each year, there are up to 225 people diagnosed in the U.S. Globally, leprosy is still found in more than 120 countries with approximately 200,000 new cases reported each year. According to the World Health Organization (WHO) the countries with the highest number of new cases are:1.2
Many countries have successfully reduced leprosy cases, with 56 countries reporting zero cases and 112 countries reporting fewer than 1,000 cases annually.
WHO defines leprosy elimination as a prevalence of less than 1 case per 10,000 people. This goal was achieved globally in 2000 and in most countries by 2010. However, the reduction in new cases has been gradual, and continued efforts are needed to stop transmission.
Leprosy is usually diagnosed clinically by a healthcare provider. Laboratory tests may be needed in difficult-to-diagnose cases.
Doctors look for three key signs to confirm leprosy:1,2
For treatment purposes, leprosy is classified into two types:1
Leprosy is completely curable with a combination of antibiotics known as multidrug therapy (MDT). MDT includes three medicines, dapsone, rifampicin and clofazimine.1,8
These medications kill the bacteria, stop transmission and cure the disease:8
Clofazimine is not available in U.S. pharmacies but can be obtained through the National Hansen’s Disease Program (NHDP).
There are small differences between the USA guidelines and the WHO guidelines regarding the duration of the treatment and the drugs that are used. Treatment depends on the type of leprosy:8
The longer treatment duration in the U.S. follows a conservative approach to ensure complete eradication of the bacteria.
Within a few days of starting treatment, a person is no longer contagious, so isolation is not necessary. Skin lesions start improving within months, but complete healing may take years. Dead bacteria remain in the body for some time, which does not mean treatment failed.8
In the United States, leprosy medication is provided free of charge by the National Hansen’s Disease Program (NHDP). Patients or doctors can call 1-800-642-2477 for assistance.
Alternative Medications (for those who cannot take standard treatment) include: 8
A newer drug, known as bedaquiline is being studied for its ability to kill leprosy bacteria faster than rifampin. Early studies show promising results.
Follow-up during treatment is as follows:8
Continuing to take medication is critical to prevent relapses or drug resistance. Patients should inspect their hands, feet and eyes daily for injuries. Protective measures (such as wearing proper footwear and gloves) can prevent injuries due to nerve damage and loss of sensation.8
Relapses are rare but if they occur it is usually 5 to 10 years after treatment. Patients should return for evaluation if new lesions appear.
Contrary to common perceptions, leprosy does not cause fingers and toes to drop off. The loss of fingers and toes that is sometimes seen is not due to the leprosy infection but to injuries that occur because of nerve damage and loss of feeling in the extremities. These injuries may become secondarily infected with other kinds of bacteria and cause the toes or fingers to lose infected bone and ultimately shorten. If the injuries can be prevented, much of the disability will not occur.2
The most important thing that can be done to prevent permanent disability is to diagnose and treat patients at the very earliest stages of the disease. They need to be started on appropriate drugs to kill the bacteria and reactions must be treated promptly if they occur. For people who already have had some nerve damage, health education in the care of hands, feet and eyes is very important to prevent further injury and deformity.2
Neuropathic pain is common and can significantly impact quality of life. Special protective shoes help prevent foot ulcers. Corrective surgery may be needed for severe deformities (clawed hands, foot drop).2
In the United States, people with Hansen’s disease can receive specialized care at federally supported clinics run by the National Hansen’s Disease Program (NHDP) with locations throughout the U.S. and Puerto Rico.
Someone needing leprosy treatment can contact the NHDP at 1-800-642-2477 for free medication and specialist care.
WHO provides MDT free of charge worldwide.
Stopping the spread of leprosy requires early detection and treatment. Contact tracing is recommended by WHO to identify close contacts of people with leprosy. A single dose of rifampicin (SDR-PEP) is given to at-risk contacts to reduce their chance of developing leprosy.
WHO provides technical support, training and research to help countries eliminate leprosy.
Their Global Leprosy Strategy 2021–2030 focuses on:
The WHO has several resources for leprosy:
For the latest data and reports, visit WHO’s Weekly Epidemiological Record.
Information on current clinical trials is posted on the Internet at https://clinicaltrials.gov/. All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Toll-free: (800) 411-1222
TTY: (866) 411-1010
Email: prpl@cc.nih.gov
Some current clinical trials also are posted on the following page on the NORD website:
https://rarediseases.org/living-with-a-rare-disease/find-clinical-trials/
For information about clinical trials sponsored by private sources, contact:
https://www.centerwatch.com/
For information about clinical trials conducted in Europe, contact:
https://www.clinicaltrialsregister.eu/
NORD strives to open new assistance programs as funding allows. If we don’t have a program for you now, please continue to check back with us.
NORD and MedicAlert Foundation have teamed up on a new program to provide protection to rare disease patients in emergency situations.
Learn more https://rarediseases.org/patient-assistance-programs/medicalert-assistance-program/Ensuring that patients and caregivers are armed with the tools they need to live their best lives while managing their rare condition is a vital part of NORD’s mission.
Learn more https://rarediseases.org/patient-assistance-programs/rare-disease-educational-support/This first-of-its-kind assistance program is designed for caregivers of a child or adult diagnosed with a rare disorder.
Learn more https://rarediseases.org/patient-assistance-programs/caregiver-respite/The information provided on this page is for informational purposes only. The National Organization for Rare Disorders (NORD) does not endorse the information presented. The content has been gathered in partnership with the MONDO Disease Ontology. Please consult with a healthcare professional for medical advice and treatment.
The Genetic and Rare Diseases Information Center (GARD) has information and resources for patients, caregivers, and families that may be helpful before and after diagnosis of this condition. GARD is a program of the National Center for Advancing Translational Sciences (NCATS), part of the National Institutes of Health (NIH).
View reportOrphanet has a summary about this condition that may include information on the diagnosis, care, and treatment as well as other resources. Some of the information and resources are available in languages other than English. The summary may include medical terms, so we encourage you to share and discuss this information with your doctor. Orphanet is the French National Institute for Health and Medical Research and the Health Programme of the European Union.
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