Leprosy: Understanding a Stigmatized Disease

March 20, 2025

Leprosy, also known as Hansen’s disease, is a long-term infectious disease that primarily affects the skin, peripheral nerves, and mucosal surfaces of the upper respiratory tract.¹ The disease produces hypopigmented or reddish skin patches, nodules, and plaques, often accompanied by loss of sensation and muscle weakness due to nerve damage. If left untreated, it can lead to permanent scarring, disfigurement, and disability.

History of Leprosy & Psychosocial Factors

Leprosy is one of the oldest known diseases that has existed since ancient civilizations. Due to the visually disturbing skin lesions, throughout history, people with leprosy faced extreme social isolation. Even in some regions, they were thrown out of cities and were labeled as ‘lepers’, a stigmatizing term. To help reduce negative perception, in 1980, the disease was renamed “Hansen’s disease”. This is why, people with leprosy need psychological help along with medical treatment.

Is Leprosy still around?

Although rare, leprosy still exists in some parts of the world. Every year, the World Health Organization reports 200,000 cases globally.² Most cases are reported from tropical regions, especially Southeast Asia as a hot and moist climate is helpful for bacterial growth.

The Cause of Leprosy

Leprosy is a transmissible disease caused by bacteria from the Mycobacterium leprae complex, which includes Mycobacterium leprae and Mycobacterium lepromatosis.³ M. leprae is the most well-known causative agent, while M. lepromatosis has been identified in some cases of diffuse lepromatous leprosy, particularly in Mexico and the Caribbean.⁴ It is a rod-shaped, extremely slow-growing bacterium that takes 12-14 days to replicate. As a result, it takes years for symptoms to appear after a person is exposed to the pathogen. Therefore, it is difficult to tell if the patient has caught the disease after exposure.

Mycobacterium laprae
(Image courtesy: Adobe Stock)

Route of Transmission

The exact means of transmission of leprosy is not fully understood, but it is most likely spread through the respiratory route. Nasal discharge from untreated patients with lepromatous (multibacillary) disease can contain large numbers of bacilli, which may be inhaled by others. Once the bacteria enter the upper respiratory tract of a new host, they can spread throughout the body. In rare cases, the bacteria may also enter through broken skin.⁵ Though it attacks multiple cells, the main targets are skin macrophages (a large cell of the immune system that engulfs foreign agents) and Schwann cells (that coat and protect nerves).

Symptoms of Leprosy

Since the disease mainly affects the skin, peripheral nerves, and mucous membrane of the nose, initial symptoms include:

Thick and dry patches on the skin that are pale from surrounding areas.
Lumps or irregular swellings specifically on the face and on the earlobe.
Loss of sensations like pain and touch in some parts of the body.

Advanced Leprosy Symptoms:

With the progression of the disease, symptoms gradually worsen. Advanced symptoms include:

Burning sensation around the body
Red, irritated patches/ nodules on the skin
Chronic skin ulcers that do not heal
Thick skin leading to scarring and shorter toes
Disfigurement of the face
Loss of eyebrows
Paralysis of hand and feet
Vision problems

Types of Leprosy

In response to the entry of pathogens, the body’s defense mechanisms activate. Depending on the severity of the disease and the extent of the immune response, the disease is generally divided into three types: ⁶

Tuberculoid Leprosy: It is a milder form that occurs in people with a good immune response. As a result, it exhibits a few mild skin lesions with few bacteria. This form is less contagious.
Lepromatous Leprosy: It occurs when the immune response is poor. The condition manifests as widespread skin lesions that are full of bacteria and extensive damage to nerves. This form of the disease is more contagious.
Borderline Leprosy: it has clinical features of both tuberculoid and lepromatous disease.

Besides this, there are two other methods that physicians use to categorize the disease.

1. Ridley-Jopling Classification:

It is a detailed system of classification built on the spectrum of clinical features and, the number of bacteria present in the skin. Hence, it gives an idea about the immune response of the body. the classification includes the following forms of leprosy:

Tuberculoid (TT)

It is a mild and less contagious form of leprosy. The patient presents with a few, flat and well-demarcated skin lesions that are of a pale or reddish color. No or little damage to nerves occurs in it.

Borderline Tuberculoid (BT)

In this type, more lesions are present than tuberculoid leprosy. These lesions are of varying sizes and have a characteristic “target” appearance. Also, nerve damage occurs with loss of sensation in some parts of the body.

Mid-Borderline (BB)

It has multiple punched-out skin lesions which means margins are elevated. They appear like raised, reddish sores with numbness in the center of the lesion. In addition, more damage to nerves occurs in this type with nerves appearing thick and loss of sensation occurring in the body.

Borderline Lepromatous (BL)

Extensive damage to skin and nerves occurs in this type. There are multiple lesions of varying sizes and shapes on the body. Damage to the nerves results in numbness and muscle weakness in larger body areas.

Lepromatous (LL)

It is the most severe form of the disease that does not regress. Hence, it can damage the skin and nerves permanently. It has numerous skin lesions of multiple types which are full of bacteria. The patient can experience hair loss, disability, and disfigurement.

Classification of different forms of leprosy. (a) Tuberculoid (TT) leprosy: this shows a leprosy lesion on the lower back that has healed spontaneously and remains only a thin scar with a complete loss of sensation. (b) Borderline tuberculoid (BT) leprosy: this shows an annular lesion on the cheek of a boy with BT. (c) Borderline borderline (BB): this shows a scarred lesion on the right cheek. (d) Borderline lepromatous (BL) leprosy: this shows a few raised and erythematous lesions on the arm of a patient. (e) Lepromatous leprosy: this leprosy patient has marked loss of the eyebrows and eyelashes and thickening of the facial skin. (The images are from the Wellcome Collection with a 4.0 International (CC BY 4.0) license)

2. WHO Classification:

Physicians use this simpler classification to evaluate and treat patients where less clinical or lab support is available. It depends on the number of lesions and bacterial load.⁷

Single lesion paucibacillary: The presence of one lesion (sore/patch) and no bacteria in skin smears.
Paucibacillary: Two to five lesions and no bacteria in skin smears.
Multibacillary: More than five lesions and bacteria are present in skin smears.

Is Leprosy Contagious?

Contrary to popular belief, leprosy is not that contagious. Since the pathogen spreads through droplets, you can only catch it if you are in close contact with an untreated patient for a prolonged time.⁸
Note: Leprosy doesn’t transmit through intercourse. Moreover, pregnant mothers do not pass on leprosy to their babies.

Complications

Delayed diagnosis, ineffective treatment, or low compliance contributes to significant complications such as:

Loss of hair
Permanent skin scarring
Weakness of muscles leading to disability
Inflammation of eyes and vision loss
Disfigurement of the face leading to a flat nasal bridge and lion-like face
Claw-like hands and/or deformed feet
Chronic nasal irritation and bleeds
Kidney failure
Erectile dysfunction and infertility

Flattening of the nasal bridge in advanced stages of leprosy. Image Credit: Flicker image, licensed under CC BY-NC 2.0

Risk Factors

Some conditions can lead to an increased risk of catching leprosy. These include:

Exposure: Close contacts like household individuals of the patient are more likely to catch the disease than others.
Genetic Probability: Due to unknown reasons, some people are genetically more susceptible to getting infected.
Age and immunity: The elderly and those having compromised immune systems are more at risk than young people.
Socioeconomic factors: The poor people living in crowded spaces and in unhygienic conditions are more vulnerable to disease.

Diagnosis of Leprosy

The first step is clinical evaluation of lesions. In most cases, it is sufficient to diagnose the disease. However, to strengthen the diagnosis, your doctor will do further tests like:

Skin Smear:

It involves taking a sample from the active lesion and looking for the presence of bacteria. It is necessary for the accurate diagnosis of disease. However, negative test results do not rule out the disease.

Biopsy:

In this, they remove a part of the infected skin or nerve and send it to the lab for further testing.⁹

Lepromin Skin Test:

It involves injecting Leprosy-causing bacteria under the skin of the forearm and the area is observed for any kind of reaction. A positive reaction confirms the diagnosis of leprosy.

PCR:

Polymerase chain reaction or PCR is a test that detects the genetic material of the organism in the tissues. ¹⁰

Serological Tests:

These are uncommon tests that doctors occasionally perform to evaluate the effectiveness of therapy.

Leprosy. Skin smear in diagnosis
(Image Courtesy: Margreet Hogeweg, Leprosy and the Eye Teaching Set (2010). Published by the International Centre for Eye Health. Image taken from Flickr, licensed under CC BY 2.0.)

Differential Diagnosis

Lesions of leprosy can be confusing and may mimic other health conditions such as:

Fungal infection
Angular psoriasis
Systemic Lupus Erythematosus
Mycosis fungoids
Neurofibromatosis
Granuloma annulare

Treatment of Leprosy

Leprosy is managed in an outpatient setting and hospitalization is not required. The physicians prescribe a WHO-recommended three-drug therapy consisting of dapsone, rifampicin, and clofazimine.¹¹

The paucibacillary form needs 6 months of treatment while the multibacillary form needs 12 months. However, in severe cases, patients may need treatment for longer periods extending up to 24 months. Additionally, they recommend anti-inflammatory agents and steroids like prednisolone to control nerve pain.

Apart from traditional drugs, minocycline, ofloxacin, and clarithromycin are currently in use as second-line therapy in rifampicin-resistant cases.¹²

Leprosy Prevention

To prevent the spread of disease, the BCG vaccine is helpful. But even in vaccinated patients, there is a chance to get infected. Alternatively, doctors recommend a single dose of dapsone for close contact with patients. According to recent studies, combining these two methods is even more beneficial.

Conclusion

Leprosy is a mythical ancient disease, which can’t kill you but harms your health and appearance significantly. It is not highly contagious and most of its forms are curable except lepromatous leprosy which can lead to considerable disfigurement and disability. Timely diagnosis and management results in better outcomes. If you see any kind of lesion on the body, seek consultation with your healthcare provider immediately.

Refrences

1
Bhandari, J., Awais, M., Robbins, B. A., & Gupta, V. (2023). Leprosy. In StatPearls. StatPearls Publishing. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK559307/
2
World Health Organization. (2025, January 24). Leprosy. Retrieved from https://www.who.int/news-room/fact-sheets/detail/leprosy
3
UpToDate. (n.d.). Leprosy: Epidemiology, microbiology, clinical manifestations, and diagnosis. Retrieved from https://www.uptodate.com/contents/leprosy-epidemiology-microbiology-clinical-manifestations-and-diagnosis?search=leprosy&source=search_result&selectedTitle=1%7E70&usage_type=default&display_rank=1#H1710007
4
Alrehaili, J. (2023). Leprosy classification, clinical features, epidemiology, and host immunological responses: Failure of eradication in 2023. Cureus, 15(9), e44767. https://doi.org/10.7759/cureus.44767
5
Fischer, M. (2017). Leprosy – an overview of clinical features, diagnosis, and treatment. Journal der Deutschen Dermatologischen Gesellschaft, 15(8), 801–827. https://doi.org/10.1111/ddg.13301
6
Chen, K.-H., Lin, C.-Y., Su, S.-B., & Chen, K.-T. (2022). Leprosy: A review of epidemiology, clinical diagnosis, and management. Journal of Tropical Medicine, 2022, Article 8652062. https://doi.org/10.1155/2022/8652062
7
World Health Organization. Classification of leprosy. WHO, Geneva 2011.
8
Ronse, M., Nieto-Sanchez, C., De Coninck, S., Verdonck, K., & Peeters Grietens, K. (2022). Definition of ‘close contacts’ in leprosy studies: Protocol for a scoping review. F1000 Research, 11, Article 808. https://doi.org/10.12688/f1000research.123862.1
9
Song, S., Lim, J., Park, S., Lee, S., Baek, J., Park, H., Roh, J. Y., & Kim, H. J. (2022). Diagnosis of new leprosy patients through various histological findings according to biopsy sites. Annals of Dermatology, 34(6), 487–489. https://doi.org/10.5021/ad.20.224
10
Martinez, A. N., Talhari, C., Moraes, M. O., & Talhari, S. (2014). PCR-based techniques for leprosy diagnosis: From the laboratory to the clinic. PLOS Neglected Tropical Diseases, 8(4), e2655. https://doi.org/10.1371/journal.pntd.0002655
11
Yang, J., Kong, J., Li, B., Ji, Z., Liu, A., Chen, J., Liu, M., Fan, Y., Peng, L., Song, J., Wu, X., Gao, L., Ma, W., Dong, Y., Luo, S., & Bao, F. (2023). Seventy years of evidence on the efficacy and safety of drugs for treating leprosy: A network meta-analysis. Journal of Infection, 86(4), 338–351. https://doi.org/10.1016/j.jinf.2023.02.019
12
Williams, D. L., Hagino, T., Sharma, R., & Scollard, D. (2013). Primary multidrug-resistant leprosy, United States. Emerging Infectious Diseases, 19(1), 179–181. https://doi.org/10.3201/eid1901.120864

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