What Is Leprosy?

Overview

Leprosy, also known as Hansen’s Disease, is a slow-onset bacterial disease affecting the nerves, skin, eyes, and inner lining of the nose. When the bacteria reach the nerves, they cause swelling under the skin, preventing some people from feeling pain and losing their sense of touch. Other symptoms include the skin becoming red, dry, and flaky. People with leprosy can become injured more easily, as they may not feel pain sensations from damage to the skin, such as cuts and burns. Each year, there are more than 200,000 leprosy cases around the world.

Types of leprosy

Why do we call the condition leprosy? It gets its name from the scientific name for the bacteria that causes it – Mycobacterium leprae.¹ There are three main types of leprosy, which are as follows: 

1. Tuberculoid leprosy – this only causes mild symptoms such as skin sores, as the body’s immune system is easily able to fight against the bacteria. 
2. Lepromatous leprosy – this causes more severe symptoms, with widespread skin sores and lesions of the nerves, skin, and organs. This is because the body’s immune system is less able to fight against the bacteria. 
3. Borderline leprosy – this results in a combination of the symptoms of Tuberculoid leprosy and Lepromatous leprosy.  

Leprosy is not highly contagious, but is thought to spread through the air, such as through coughs and sneezes. It is not spread through skin-to-skin contact, sexual activity, pregnancy, or being close to people. However, it is worth noting that most people do not get ill from the bacteria that cause leprosy, as their immune systems can fight it off; but five per cent of people do get ill. 

Who gets leprosy? 

The World Health Organisation (WHO) classifies Leprosy as a Neglected Tropical Disease. This means it is one of 18 diseases worldwide that meets the following three criteria: 

1. Affects the poorest individuals
2. Is usually chronic 
3. Can cause severe inflammation-related pain and disability²

Whilst the WHO eliminated leprosy as a global public health problem in 2000  – as it is rare and affects less than one in 10,000 people – countries such as Brazil, India, and Indonesia reported more than 10,000 cases in 2019. You can read which other countries still report leprosy cases today here. 

Leprosy is most common in those aged 5 to 15 years and those aged over 30. 

As the bacteria behind leprosy grow in living hosts such as humans and thrive in tropical regions, the disease can be carried by some armadillos native to South America and Mexico, putting those living in these regions at a higher risk.

Signs and symptoms of leprosy

The name leprosy is derived from the Greek word ‘lepros’, meaning scaly, as this is how it appears on the skin.¹ The first skeletal evidence of leprosy dates as far back as 2000 BCE, believed to originate from India, and later spreading through West Asia, Syria and Rome. 

The main symptoms of leprosy are as follows:³ 

• Thick discoloured plaques on the surface of the skin 
• Nerve damage near the area of skin damage 
• Loss of sensation in the hands and feet 
• Pain and tenderness in nerves
• Asymmetrical patches of injured skin 

Untreated leprosy can lead to the following symptoms: 

• Paralysis of the hands and feet 
• Loss of eyebrow hair 
• Loss of affected limbs such as toes and fingers
• Disfigurement of the nose 

Diagnosis

To diagnose leprosy, your healthcare provider will need to take a skin biopsy,⁴ which usually involves making an excision in the skin to obtain a tissue sample. The skin sample will then be stained to show if bacteria are present. Then a molecule called lepromin is injected into the sample, which contains inactivated leprosy to trigger an immune response. Lepromin is a type of antigen, a flag showing the immune system there is an infection. The type of immune response triggered will identify which type of leprosy a person has, due to which type of molecules called antibodies that are released. 

Laboratory scientists may also use a technique called Polymerase Chain Reaction (PCR), which involves using sticky sections of synthetic DNA to target a specific segment of the bacterial DNA so that lots of copies can be made and studied to confirm it is the bacteria associated with leprosy. As PCR tests can be expensive and aren’t accessible in some countries, a blood test can be performed to identify the presence of antibodies known as PGL-1, which the body uses to fight leprosy infections. 

Management and treatment for leprosy

As leprosy is a bacterial infection, it is treated with antibiotics. However, as antibiotics are used for a range of conditions, bacteria can learn methods to stop these medicines from working, by learning how they act. This is known as antibiotic resistance. So, healthcare providers can prescribe multiple different antibiotics, usually two or three together that use different methods to fight bacteria. This is known as multidrug therapy. You can think of it as having multiple different weapons in your armoury to fight off the bacteria. 

The complications of leprosy such as nerve damage cannot directly be treated using antibiotics. So, painkillers such as Gabapentin and Pregabalin are used.⁵ In more severe cases of nerve pain, opioids such as Lidocaine and Morphine may be used. 

The history of leprosy 

Leprosy is an ancient disease with a rich history. In medieval times, people with leprosy were cast out of society into quarantined areas due to social stigma about its contagiousness.⁶ You would even be isolated by your own family. This came to an extreme when celebrations would be held to mark the death of quarantined individuals.

Through the Middle Ages, leprosy cases declined steadily due to the rise of some of history's most abhorred diseases: syphilis, tuberculosis and the bubonic plague. Whilst many of these diseases competed with one another, the bacterium behind Tuberculosis, Mycobacterium tuberculosis, actually protected individuals against leprosy!

Over time, improvements in living conditions and medicine contributed to leprosy becoming a rare and treatable disease. Since leprosy’s discovery by the Norwegian scientist Gerhard-Henrik Armauer Hansen in 1874, medicine has developed considerably to understand antibiotics and successfully treat leprosy. But it remains one of the most stigmatised medical conditions. So, what can be done about this?

Fighting leprosy stigma

The Leprosy Mission charity in England and Wales promotes education and awareness to fight discrimination against, and marginalisation of, those with leprosy. You can read about their support and advocacy work here. 

World Leprosy Day is celebrated every year on the last Sunday in January and January 30th in India. The day is a chance to spread awareness about the fact leprosy is curable and that those with leprosy deserve inclusion and dignity. You can read about the goals and theme of the 2023 World Leprosy Day here. 

FAQs

How can I prevent leprosy?

The infographic below shows some key ways to prevent the spread of leprosy:

Image source: Parr-Reid S. Canva. 

How common is leprosy?

Leprosy is considered a neglected tropical disease, as it affects less than one in 10,000 people globally. It still occurs in 120 countries, with Brazil, India and Indonesia being the most affected and over 200,000 people being diagnosed each year. 

Who is at risk of leprosy?

Generally, the age at diagnosis for leprosy is between 5 and 15 or after 30. The pie chart below shows the proportion of leprosy cases by world region from 2021:⁷ 

Image source: Parr-Reid S. Microsoft Excel. 

What can I expect if I have leprosy?

Leprosy causes symptoms such as skin lesions, swelling under the skin and nerve damage.³ This nerve damage can prevent you from feeling pain, so may put you at a higher risk of injuries such as cuts or burns. The condition is diagnosed with a procedure called a biopsy, where a sample of your skin is taken and tested in a laboratory. Treatment for a leprosy patient involves taking a combination of three different antibiotics, to ensure that you are protected as much as possible from the bacteria that cause leprosy. 

Is leprosy contagious?

Leprosy is not highly contagious but can spread between individuals through droplets such as in coughs and sneezes. As there are different types and severity of leprosy, it is important to consult your healthcare provider to discuss its spread if you or someone you know is diagnosed with leprosy. 

When should I see a doctor?

If you have been in close contact with someone with untreated leprosy or have symptoms such as skin lesions, swelling under the skin, asymmetrical plaques on the skin, loss of sensation in hands and feet and nerve pain, then it is important to speak with your healthcare provider.³ This will help to ensure that the condition does not become advanced and can be treated easily. If you are worried or anxious about visiting your healthcare provider, it can help to bring a friend or family member along with you for support. 

Summary

Leprosy is a chronic bacterial disease spread through airborne droplets such as those found in coughs and sneezes. It leads to inflammation, skin lesions and nerve damage, meaning those with the condition may not feel pain. It is considered rare and usually affects those aged 5–15 and over 30. It's most common in tropical regions such as South America and Mexico, as well as less economically developed regions such as Indonesia and India. The condition is diagnosed with a simple skin biopsy to test a sample of skin tissue for the bacteria. Leprosy is treated with multidrug therapy, using three antibiotics to prevent antibiotic resistance.