What Is Leprosy (Hansen's Disease)?

Leprosy, or Hansen’s disease, is a chronic infectious disease caused by the Mycobacterium leprae bacteria. It can affect the skin, nerves of the hands and feet, eyes, and lining of the nose.

After contracting leprosy, it can take up to 5-7 years for symptoms to develop. The first symptom is usually a spot (lesion) on the skin that is reddish-colored or lighter than your normal skin tone. As the disease progresses, leprosy can cause nerve damage, leading to numbness, muscle weakness, disfigurement, and blindness. Leprosy is curable with multi-drug therapy (antibiotics) taken over one to two years.

Each year, more than 200,000 people worldwide are diagnosed with leprosy. It is particularly rare in the United States, affecting up to 250 people annually. Early diagnosis and treatment can help prevent complications and the spread of the disease. 

Types

There are different ways to classify leprosy types. The most appropriate treatment regimen can be determined once the type of leprosy a person has is found.

Traditional Classification

The traditional classification of leprosy types is based on the affected person’s immune response and the number of Mycobacterium leprae bacteria in the body. Traditional leprosy classification types include:

• Tuberculoid leprosy: This is the mildest form of leprosy, found in people whose bodies can fight it with a strong immune response and who have relatively few bacteria in their bodies. They typically have a few well-defined skin lesions and possible nerve damage in the affected areas.
• Borderline leprosy: This type of leprosy is more severe than tuberculoid leprosy, with more bacteria in the skin and nerves of those affected. People with borderline leprosy often have several skin lesions and some nerve damage. 
• Lepromatous leprosy: This is the most severe form of leprosy. People with weakened immune systems are more vulnerable to this type, which typically causes widespread skin lesions, nerve damage, and other symptoms.

Simplified Classification

The World Health Organization (WHO) uses a simplified classification system that divides leprosy into two categories: paucibacillary (PB) and multibacillary (MB). This system determines leprosy types based on the number of skin lesions and nerves affected by the infection. 

• Paucibacillary leprosy: Five or fewer skin lesions and one or no nerves affected.
• Multibacillary leprosy: Six or more skin lesions and one or more nerves affected.

Leprosy Symptoms 

Symptoms of leprosy can develop within one year after contracting the bacteria but may take as many as 20 years to emerge. On average, symptoms develop five years after the infection has been contracted. Leprosy primarily affects the skin, nerves in the hands and feet, and mucous membranes of the upper respiratory tract (inner lining of the nose). 

Skin Symptoms 

Leprosy symptoms on the skin include: 

• Pale or reddish patches (lesions) that may be numb 
• Bumps (nodules) 
• Thickened, dry, or stiff skin 
• Painless sores on the bottom of the feet 
• Lumps or swelling on the face and ears 
• Hair loss (primarily the eyelashes and eyebrows) 
  

Nerve Symptoms 

Leprosy can affect the peripheral nerves (the nerves around the brain and spinal cord that send information to the rest of your body) in the hands and feet, causing symptoms such as:

• Numbness on the affected areas of the skin 
• Muscle weakness or paralysis (loss of movement and sensation) in the hands and feet 
• Vision problems, including blindness 
• Loss of reflexes 
• Pain and tenderness in the affected areas 
• Deformities in the hands and feet, such as curling of the fingers and toes

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Other Symptoms 

When leprosy affects the nasal mucosa (inner lining of the nose), it can lead to symptoms such as:

• Chronic nasal congestion
• Nosebleeds
• Nose disfigurement, including total or partial loss of the nose

What Causes Leprosy? 

Leprosy is caused by a slow-growing bacteria called Mycobacterium leprae. The bacteria spread from person to person through respiratory droplets through the nose and mouth. Though leprosy is contagious, it typically only spreads through close and frequent contact with someone with untreated leprosy. About 95% of the world’s population has a natural immunity to leprosy.

When someone contracts leprosy, the bacteria invade and multiply within the body’s cells. The immune system plays a crucial role in determining whether someone will develop symptoms and how the disease progresses. Some people have a strong immune response against the bacteria, which can limit the spread of the infection and result in milder forms of leprosy. Others may have a weaker immune response, leading to more severe forms of the disease.

Risk Factors 

Most people have a natural immunity to leprosy. When you have natural immunity, you won't be affected by the infection, even if you're exposed to the bacteria that causes the disease. In those without immunity, certain risk factors can increase the likelihood of developing leprosy, including:

• Having a weakened immune system due to an underlying condition, such as HIV/AIDS, diabetes, or heart disease
• Exposure to (touching) wild armadillos, which can carry the disease
• Prolonged, frequent close contact with a person who has untreated leprosy 
• Living in or traveling to regions where leprosy is more common (e.g., Brazil, Ethiopia, Nepal) 

Diagnosis

Leprosy is diagnosed through a physical examination, medical history and symptom review, and diagnostic tests. Healthcare providers order these tests to help confirm the presence of the Mycobacterium leprae bacteria and determine the type of leprosy you have. 

Commonly used diagnostic tests for leprosy include:

• Skin exam: Healthcare providers look for skin lesions, such as pale or reddish patches on the skin, bumps, nodules, and thickened skin. They also look for signs of nerve damage, such as numbness, tingling, weakness, and paralysis.
• Skin smear: A tiny cut is made in the skin, and fluid from the cut tissue is collected and examined under a microscope to confirm the presence of Mycobacterium leprae bacteria.
• Skin biopsy: A sample is removed from a skin lesion and examined under a microscope to look for leprosy bacteria.
  

Once the diagnosis is confirmed, a lepromin skin test may be performed. For this test, a small amount of Mycobacterium leprae protein is injected into the skin. The injection site is examined three days later and then again 28 days later. If a person has a reaction to the test, such as redness and swelling, this confirms the leprosy diagnosis and helps determine which type.

Treatments for Leprosy 

Treatment for leprosy is generally highly effective and can cure the disease. Early treatment is ideal to help prevent complications. Treatment varies depending on the type of leprosy and the severity of symptoms.

Antibiotics

The standard treatment for leprosy is a combination of three antibiotics—usually Lamprene (clofazimine), Aczone (dapsone), and Rifadin (rifampicin)—called multi-drug therapy (MDT). MDT can cure leprosy, but it must be taken for the entire course of treatment, which is usually one to two years.

How long treatment is required depends on the type of leprosy a person has. People with paucibacillary leprosy (PB) typically need to take MDT for six months to a year. Treatment for multibacillary leprosy (MB) usually lasts two years.

Supportive Therapies 

People with leprosy may also need treatment for nerve damage, skin lesions, and other complications. These treatments may include: 

• Pain management: If nerve damage or pain is an issue, pain relievers (e.g., gabapentin, a medication used to treat nerve pain) may help reduce pain and discomfort.
• Wound care: People with skin lesions, especially open sores or ulcers, may need wound care to prevent secondary infection and promote healing.
• Orthopedic devices: People with nerve damage may need to wear splints or braces to support weakened limbs.

Prevention

You can lower your risk of leprosy by:

• Avoiding close, frequent contact with someone who has untreated leprosy 
• Avoiding contact with wild armadillos 
• See a healthcare provider if you have been exposed to leprosy or are at a high-risk of developing the disease. Post-exposure prophylaxis (treatment to prevent the onset of disease) involves taking a single dose of an antibiotic (rifampicin) to help kill the bacteria that causes leprosy. 

Complications 

Leprosy is a progressive disease that can lead to complications, especially if left untreated. Possible complications of leprosy include:

• Nerve damage, which may cause numbness, tingling, weakness, and paralysis 
• Skin ulcers
• Vision problems, including glaucoma or blindness 
• Joint pain 
• Muscle weakness
• Hands and feet deformities 
• Facial deformities 
• Erectile dysfunction 
• Infertility 
• Kidney failure

A Quick Review

Leprosy (Hansen’s disease) is a chronic infectious disease caused by the Mycobacterium leprae bacteria, which spreads from person to person through respiratory droplets. It is not highly contagious and usually only spreads after prolonged, frequent contact with someone who has it.

Symptoms can take years to develop after exposure and may include discolored spots on the skin, loss of sensation in hands and feet, and muscle weakness. Left untreated, leprosy can lead to complications, including disfigurement and blindness. Multi-drug therapy (MDT) with antibiotics can cure leprosy. Early diagnosis and treatment is the best way to prevent complications.