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Leprosy (Hansen’s Disease)

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Iqra Mazhar

Overview

From the Bible to the Hindu Vedas, several religious texts have referenced leprosy, describing it as a disfiguring skin disease. Based on human remains found in India, archaeologists have dated the disease back to 2000 BC<a href="#accordion">[1]</a>. Historians predict that the army of Alexander the Great contracted the infection and carried it from India, through the Middle East, to the Eastern Mediterranean<a href="#accordion">[1]</a>. Later as Roman emperors waged wars, soldiers spread the disease across Europe.

The World Health Organization (WHO) defines leprosy as a chronic infectious disease affecting the skin, eyes, nerves, and nasal mucosa<a href="#accordion">[2]</a>. It results from an infection with the slow-growing bacteria Mycobacterium leprae. Labeled as a neglected tropical disease, the ancient skin condition has affected people for centuries.&nbsp;

In 2020, there were 127,558 global leprosy cases, of which more than 8,000 occurred in children less than 15 years<a href="#accordion">[2]</a>. Approximately 80% of the new global cases come from India, Brazil, and Indonesia<a href="#accordion">[3]</a>. High-income countries, like the United States, report approximately 150 new cases every year<a href="#accordion">[4]</a>.&nbsp;According to the WHO Global Leprosy Update, Pakistan had a registered prevalence of 353 cases at the end of 2020<a href="#accordion">[5]</a>. Moreover, the disease is endemic in the Northern areas of the country<a href="#accordion">[6]</a>.&nbsp;

Although the global prevalence has been falling, in several low-income countries the disease remains a major public health concern. Moreover, despite the availability of treatments, multiple stigmas and misconceptions continue to surround leprosy. As a result, those affected by the condition may often face discrimination, loss of employment, or even isolation from society. Therefore, to erase these social stigmas, leprosy is also called Hansen&rsquo;s disease, named after the Norwegian physician that discovered M. Leprae.&nbsp;

<div>&nbsp;</div>

Leprosy can be classified based on the number of skin lesions, nerve involvement, and the presence of the bacteria on a slit-skin smear. Several classification approaches exist for the disease. According to one classification, leprosy can be divided into: 
&nbsp;

<ul>
	<li>Tuberculoid - This is a mild form of leprosy characterized by a few skin lesions with mild nerve damage in the affected area of the skin. Compared to lepromatous leprosy, it is less contagious.</li>
	<li>Lepromatous - A more severe form of the disease, people with this type of leprosy have widespread lesions affecting the skin, nerves, and organs. People with a poor immune system typically develop this particular type. Moreover, it is more contagious than other forms of leprosy.</li>
	<li>Borderline - In borderline leprosy, symptoms of both tuberculoid and lepromatous leprosy are present. It is also called dimorphous leprosy.&nbsp; 
	&nbsp;</li>
</ul>

The WHO divides the disease into two categories<a href="#accordion">[7]</a>. These include:

<ul>
	<li>Paucibacillary - The patient has 1 to 5 skin lesions, and no bacteria is detected in the skin smear.</li>
	<li>Multibacillary - The patient will have more than five skin lesions or nerve involvement, or a slit-skin smear will demonstrate the presence of the bacterium. 
	&nbsp;</li>
</ul>

Another classification, the Ridley-Jopling system, classifies the disease based on the severity of symptoms<a href="#accordion">[3]</a>:

<ul>
	<li>Tuberculoid Hansen&rsquo;s Disease - This is characterized by a few skin lesions which may be large; nerve involvement may cause numbness in the area. It typically heals on its own. However, in some cases, it may progress to a more severe form.&nbsp;</li>
	<li>Borderline Tuberculoid Hansen&rsquo;s Disease - Similar to tuberculoid, the lesions are flat, but more in number. There is also more nerve involvement.&nbsp;</li>
	<li>Mid-Borderline Hansen&rsquo;s Disease - In this form of leprosy, the skin lesions are more numerous. Large, reddish plaques may appear on the limbs; the skin lesions may be accompanied by numbness, swollen lymph nodes, and nerve involvement. This is the most common form of leprosy.</li>
	<li>Borderline Lepromatous Hansen&rsquo;s Disease - Numerous flat lesions, plaques, bumps, and nodules may be present. There is also greater numbness experienced by the patient.</li>
	<li>Lepromatous Hansen&rsquo;s Disease - This form of leprosy has the worst prognosis. It is characterized by widespread lesions of the skin, eyes, nerves, organs, nasal mucose, and lymph nodes. Moreover, the patient may also experience hair loss, peripheral nerve thickening, limb weakness, and disfigurement.&nbsp; 
	&nbsp;</li>
</ul>

There is also another form of Hansen&rsquo;s disease called indeterminate Hansen&rsquo;s disease. It is a very early-stage form where the person may only have one skin lesion with slight numbness to touch. Moreover, it can either resolve completely or progress to any one of leprosy forms part of the Ridley-Jopling system.

<div>&nbsp;</div>

Signs And Symptoms

The word leprosy is derived from the Greek word &lsquo;l&eacute;prā&rsquo;, which translates to &lsquo;disease that makes the skin scaly&rsquo;. Although skin changes are characteristic of leprosy, in 90% of people, numbness is the first symptom to develop<a href="#accordion">[8]</a>. People may experience a loss of, or decreased sensation to, temperature, touch and pain, or pressure. Later on, skin changes may begin to manifest. They typically begin as painless, pale, or pink-coloured patches of skin which may be numb to pain or temperature.

&nbsp;

Other skin changes include:

<ul>
	<li>Thick or stiff skin; especially of the face (leonine facies), ear, and hand</li>
	<li>Redness due to inflammation</li>
	<li>Nodules on the skin</li>
	<li>Burning sensation</li>
	<li>Chronic, painless, nonhealing ulcers on the soles of the feet</li>
	<li>Painless lumps or swellings on the face or earlobes</li>
	<li>Numbness and tingling sensation in the hands and feet (paraesthesia)</li>
	<li>Loss of eyelashes or eyebrows 
	&nbsp;</li>
</ul>

Nerve damage occurs in approximately 30% of people affected with leprosy<a href="#accordion">[9]</a>. This nerve damage may result in:

<ul>
	<li>Muscle weakness or paralysis</li>
	<li>Clawed hands or foot drop due to peripheral nerve damage</li>
	<li>Vision loss&nbsp;</li>
	<li>Bone and joint deformities</li>
	<li>Nose disfigurement</li>
	<li>Enlarged peripheral nerves, especially in the elbow and knees 
	&nbsp;</li>
</ul>

Along with skin changes and numbness, people can also develop:

<ul>
	<li>Nasal congestion and nosebleeds due to involvement of the nasal mucosa</li>
	<li>Dry scalp</li>
	<li>Speech changes</li>
</ul>

<div>&nbsp;</div>

Causes

While religious scriptures associate Leprosy with sin and God&rsquo;s displeasure, thanks to Dr. Hansen&rsquo;s discovery it is clear that the causative organism is Mycobacterium leprae (M. leprae). The slow-growing pathogen cannot be cultured in vitro. However, researchers have been successful in growing them in armadillos and mice. Armadillos are also a large natural reservoir of M. leprae and have caused infections in humans across the United States<a href="#accordion">[10]</a>.

Approximately 95% of people that come in contact with the bacteria, don&rsquo;t develop the disease<a href="#accordion">[7]</a>. Since M. leprae grows slowly, symptoms can take up to 20 years to show in some people.

Despite earlier claims, it has now become clear that leprosy is not a highly contagious disease. Instead, prolonged, close contact with infected individuals is required for transmission. Researchers predict that inhalation of infected airborne droplets, produced during coughing or sneezing, is the main route of transmission.

&nbsp;

The following does not cause the disease to spread from person to person:

<ul>
	<li>Shaking hands</li>
	<li>Hugging</li>
	<li>Sitting next to an infected person</li>
	<li>Eating together</li>
	<li>Sexual contact&nbsp;</li>
	<li>Pregnancy (the disease cannot pass from the mother to the fetus)</li>
</ul>

Furthermore, people taking treatment for the disease are not considered contagious.&nbsp;

&nbsp;

Although armadillos have also been known to spread the disease to humans, the exact mechanism remains unclear.

&nbsp;

There are no screening tests for leprosy. However, in countries where the disease is endemic, annual screening of close contacts is recommended<a href="#accordion">[11]</a>. Doctors may conduct yearly physical examinations of the close contacts to check for any signs and symptoms of leprosy. 
&nbsp;

Diagnosis

According to WHO, at least one of the following must be present for a leprosy diagnosis<a href="#accordion">[7]</a>:

<ul>
	<li>Definite loss of sensation in a hypopigmented or pink skin patch</li>
	<li>Peripheral nerve thickening or enlargement with loss of sensation and/or weakness of the innervated muscles</li>
	<li>Presence of acid-fast bacilli in a slit-skin smear</li>
</ul>

This does not include patients who have already completed a course of treatment.&nbsp; 
&nbsp;

A leprosy diagnosis is based on the person&rsquo;s clinical presentation and the results of various laboratory tests. These include:

<ul>
	<li>Biopsy - A small sample of the skin lesion or the nerve is sent for examination, to assess for the presence of M. leprae. Doctors may also conduct a slit-skin smear test; this involves collecting the sample from a tiny cut in the skin lesion. In the case of multibacillary leprosy, patients will demonstrate the acid-fast bacilli in the skin samples. Whereas in paucibacillary leprosy, there will be no bacteria present.</li>
	<li>Lepromin Skin Test - This test is not diagnostic, but it can assess what type of leprosy the patient has. A small amount of inactive leprosy-causing bacteria is injected under the skin of the forearm. The injection site is assessed for a response on day 3 and then 28 days later. A positive response (&gt;5mm) means the person likely has tuberculoid or borderline tuberculoid leprosy. People with lepromatous leprosy will not react to the test.&nbsp;</li>
	<li>Polymerase Chain Reaction (PCR) - In some cases, a PCR may be used to identify M. leprae DNA in nasal smears, skin biopsy samples, and blood and tissue samples. It is mostly reserved for people with an atypical clinical presentation.</li>
</ul>

<div>&nbsp;</div>

Treatment

In the 1950s, researchers introduced dapsone for the treatment of leprosy. However, as antibiotic resistance to the drug increased, the WHO introduced a multidrug regimen for the disease<a href="#accordion">[7]</a>. It includes: 
&nbsp;

<ul>
	<li>Dapsone - The antibiotic works by inhibiting bacterial growth. It is also used to treat skin disorders such as dermatitis herpetiformis and acne. Common side effects include nausea and loss of appetite. However, severe side effects such as liver damage, hemolytic anaemia, and hypersensitivity reactions can also occur. 
	&nbsp;</li>
	<li>Rifampicin - Also known as rifampin, the drug is also used to treat tuberculosis. The antibiotic works by inhibiting bacterial DNA-dependent RNA synthesis. Common side effects include nausea, vomiting, red discolouration of urine and other bodily fluids, rash, and elevated liver enzymes.&nbsp; 
	&nbsp;</li>
	<li>Clofazimine - The drug prevents bacterial replication and is used in combination with dapsone and rifampicin to treat leprosy. Common side effects include dry skin, abdominal pain, diarrhoea, change in skin colour, and increased sensitivity to the sun. 
	&nbsp;</li>
</ul>

For paucibacillary leprosy, a treatment duration of 6 months is recommended. Whereas, in the case of multibacillary leprosy, the multi-drug treatment is taken for 12 months.&nbsp;

In the case of rifampicin-resistant leprosy, the WHO recommends treating with daily clofazimine and at least two second-line drugs, for 6 months<a href="#accordion">[7]</a>. This is followed by clofazimine plus one of the drugs for an additional 18 months. The second-line drugs include clarithromycin, minocycline, and quinolone. Moreover, in some cases, anti-inflammatory medications such as steroids and thalidomide may also be prescribed.&nbsp; 
&nbsp;

Note: Although leprosy is curable, treatment cannot reverse nerve damage. Therefore, early diagnosis and prompt treatment are key to preventing disabilities associated with leprosy.&nbsp;

<div>&nbsp;</div>

The disease is rarely fatal. However, if left untreated, it can result in severe complications. These include: 
&nbsp;

<ul>
	<li>Secondary infections</li>
	<li>Crippling of hands and feet</li>
	<li>Shortening and deformation of toes and fingers</li>
	<li>Facial disfiguration</li>
	<li>Hair loss</li>
	<li>Permanent nerve damage in limbs&nbsp;</li>
	<li>Blindness</li>
	<li>Iritis</li>
	<li>Glaucoma</li>
	<li><a href="https://www.merisehat.pk/disease/infertility-in-men" target="_blank">Infertility </a>and <a href="https://www.merisehat.pk/disease/erectile-dysfunction-90" target="_blank">erectile dysfunction</a> in men</li>
	<li>Kidney failure 
	&nbsp;</li>
</ul>

Often, people can develop reversal reactions while undergoing treatment. These include:

<ul>
	<li>Lepra Type 1 Reaction - This is a delayed-type hypersensitivity reaction that occurs in patients with borderline leprosy undergoing treatment. Patients may develop new skin lesions, neuritis, oedema, and inflammation. Additionally, there can also be sensory and motor loss. Nonsteroidal anti-inflammatory drugs (NSAIDs) and steroids are typically prescribed to these patients.</li>
	<li>Erythema Nodosum Leprosum (ENL) - Also called lepra type 2 reaction, this complication arises in patients with lepromatous leprosy. It is characterized by multiple inflamed subcutaneous nodules along with fever, arthritis, malaise, lymphadenopathy, and neuritis. Aspirin, prednisone, or thalidomide may be prescribed in the case of ENL.</li>
	<li>Lucio Phenomenon - This is a severe complication of multibacillary leprosy and is treated with systemic steroids. It is characterized by blue hemorrhagic plaques and severe ulcerations with necrosis.&nbsp;</li>
</ul>

<div>&nbsp;</div>

Prolonged, close contact with an infected person, who is not currently undergoing treatment, is the greatest risk factor for developing leprosy. Other risk factors include: 
&nbsp;

<ul>
	<li>Living in an endemic region</li>
	<li>Poverty</li>
	<li>Malnutrition</li>
	<li>Armadillo contact</li>
	<li>Immunosuppression</li>
</ul>

<div>&nbsp;</div>

The best prevention strategy is to avoid close contact with untreated infected individuals. Post-exposure prophylaxis (PEP) is recommended for close contact with leprosy patients who may be at risk of developing the disease<a href="#accordion">[11]</a>. Close contact is defined as exposure of 20 hours or more per week for more than 3 months. A single dose of rifampicin is given to these contacts, provided they are more than 2 years of age and don&rsquo;t have a history of any liver or kidney disorder.

The Bacillus Calmette&ndash;Gu&eacute;rin (BCG) vaccine has also been shown to protect against leprosy. Therefore, the WHO recommends administering the vaccine at birth in endemic countries with a high number of TB and leprosy cases<a href="#accordion">[12]</a>.

<div>&nbsp;</div>

LepVax is a leprosy vaccine currently undergoing clinical trials. The recombinant vaccine has been developed specifically for leprosy. Recently, researchers tested the vaccine among adult participants living in a leprosy-endemic country<a href="#accordion">[13]</a>. According to the phase 1 trial, the vaccine not only induced an immune response in the participants but also did not cause any adverse side effects.

&nbsp;

Key Points

<ul>
	<li>Leprosy, also called Hansen&rsquo;s disease, is a chronic infectious disease caused by the bacteria Mycobacterium leprae.</li>
	<li>Prolonged, close contact with an infected individual can transmit the infection among people.</li>
	<li>Researchers predict that inhalation of infected airborne droplets is the most likely mode of transmission. Hugging, shaking hands, sitting together, and having sexual contact cannot transmit leprosy.</li>
	<li>The disease mostly affects the skin, peripheral nerves, eyes, and nasal mucosa. It typically presents as a painless, red, or hypopigmented, skin patch that may be numb to pain or temperature. Other symptoms include thickening of facial skin, nodules, painless ulcers on the soles of feet, inflammation, paresthesia, muscle weakness, and nasal congestion.&nbsp;</li>
	<li>If left untreated, complications such as paralysis, blindness, infertility, kidney failure, permanent nerve damage, and joint deformity.&nbsp;</li>
	<li>The disease is diagnosed based on a person&rsquo;s history and clinical presentation. Additionally, a skin biopsy and lepromin test may also be conducted.&nbsp;</li>
	<li>The World Health Organization recommends a multi-drug treatment comprising dapsone, rifampin, and clofazimine. Depending on the type of leprosy, the patient may be required to take the treatment for 6-12 months.&nbsp;</li>
	<li>Leprosy is a notification priority disease, and all suspected and confirmed cases should be reported to relevant health authorities.</li>
</ul>

<div>&nbsp;</div>

[1] Santacroce, L., Del Prete, R., Charitos, I. A., & Bottalico, L. (2021). Mycobacterium leprae: A historical study on the origins of leprosy and its social stigma. Le infezioni in medicina, 29(4), 623–632.

[2] World Health Organization. (2022, January 11). Leprosy. WHO | World Health Organization.

[3] Sarode, G., Sarode, S., Anand, R., Patil, S., Jafer, M., Baeshen, H., & Awan, K. H. (2020). Epidemiological aspects of leprosy. Disease-a-Month, 66(7), 100899.

[4] CDC. (2017, February 10). What is Hansen’s Disease? | Hansen's Disease (Leprosy).

[5] World Health Organization. Global leprosy update, 2021. Weekly Epidemiological Record, 2021; 96: 421-444.

[6] Khokhar, A. R., Abdul Majeed Cheema, Abdul Sattar, Naghmana Lateef, Mujahid Hussain, & Qurrat-ul-Ain Rehman. (2020). Indigenous leprosy in Dera Ghazi Khan Division, Punjab, Pakistan. Journal of the Pakistan Medical Association, 1–11.

[7] Guidelines for the diagnosis, treatment and prevention of leprosy. New Delhi: World Health Organization, Regional Office for South-East Asia; 2017. Licence: CC BY-NC-SA 3.0 IGO.

[8] DermNet NZ. (2003). Leprosy (Hansen disease). DermNet NZ.

[9] Reinar LM, Forsetlund L, Lehman LF, Brurberg KG. Interventions for ulceration and other skin changes caused by nerve damage in leprosy. Cochrane Database of Systematic Reviews 2019, Issue 7. Art. No.: CD012235.

[10] Truman, R. W., Singh, P., Sharma, R., Busso, P., Rougemont, J., Paniz-Mondolfi, A., Kapopoulou, A., Brisse, S., Scollard, D. M., Gillis, T. P., & Cole, S. T. (2011). Probable zoonotic leprosy in the Southern United States. New England Journal of Medicine, 364(17), 1626–1633.

[11] Leprosy/Hansen disease: Contact tracing and post-exposure prophylaxis. Technical guidance. New Delhi: World Health Organization, Regional Office for South-East Asia; 2017. Licence: CC BY-NC-SA 3.0 IGO.

[12] World Health Organization (June 2018). "BCG vaccine: WHO position paper, February 2018 – Recommendations". Vaccine. 36 (24): 3408–10.

[13] Duthie, M. S., Frevol, A., Day, T., Coler, R. N., Vergara, J., Rolf, T., Sagawa, Z. K., Marie Beckmann, A., Casper, C., & Reed, S. G. (2020). A phase 1 antigen dose escalation trial to evaluate safety, tolerability and immunogenicity of the leprosy vaccine candidate LepVax (LEP-F1 + GLA–SE) in healthy adults. Vaccine, 38(7), 1700–1707.