Published: 18 Jun 2025

ICD9: 030.9      ICD10: A30.9      ICD11: 1B20

Leprosy, also known as Hansen's disease (HD), is a chronic infectious disease caused by the bacterium *Mycobacterium leprae*.
It primarily affects the skin, peripheral nerves, mucosa of the upper respiratory tract, and the eyes.

Here's a breakdown of key aspects of leprosy/Hansen's disease:

Cause:

*Mycobacterium leprae* is the causative agent. It's a slow-growing bacterium that thrives in cooler temperatures, which explains its affinity for the skin and peripheral nerves.

Transmission:

Leprosy is *not* highly contagious.
It's thought to be spread through respiratory droplets from the nose and mouth, during close and frequent contact with untreated individuals. Prolonged, repeated contact is generally required.
The exact mechanisms of transmission are still being studied.
Importantly, the vast majority of people exposed to *M. leprae* do not develop the disease because their immune systems are able to fight off the infection.

Symptoms:

The symptoms of leprosy can vary widely, depending on the type of leprosy and the individual's immune response. Common symptoms include:

Skin lesions: These are usually the most obvious sign. They can be:
Flat, discolored patches of skin (often lighter than the surrounding skin in darker-skinned individuals, or reddish/copper-colored in lighter-skinned individuals).
Nodules (bumps) on the skin.
Thickened, dry, or stiff skin.
Painless ulcers on the soles of the feet or palms of the hands.
Nerve damage: This is a hallmark of leprosy and can lead to:
Numbness or decreased sensation in the affected areas (skin lesions, hands, feet). This is often one of the earliest symptoms.
Muscle weakness, especially in the hands and feet.
Enlargement of peripheral nerves (which may be palpable).
Paralysis.
Other potential symptoms:
Eye problems (e.g., dryness, decreased blinking, glaucoma, iritis).
Nasal stuffiness or nosebleeds.
Weakness and fatigue.

Types of Leprosy:

Leprosy is classified into different types based on the immune response of the individual and the number of bacteria present in the body. The two main classifications are:

Paucibacillary (PB) leprosy: Few bacteria are present. It involves one to five skin lesions and usually one nerve involved. It tends to be milder.
Multibacillary (MB) leprosy: Many bacteria are present. It involves more than five skin lesions and multiple nerves may be involved. It can be more severe and lead to more complications if untreated.

There are other classifications, like borderline tuberculoid, borderline borderline, and borderline lepromatous, which represent a spectrum between the two poles.

Diagnosis:

Diagnosis is based on clinical signs (skin lesions, nerve damage), a skin biopsy (to detect *M. leprae*), and sometimes nerve biopsies.

Treatment:

Leprosy is curable with multidrug therapy (MDT). MDT regimens typically involve a combination of antibiotics, such as dapsone, rifampicin, and clofazimine.
The duration of treatment depends on the type of leprosy (PB or MB). PB leprosy is treated for 6 months and MB leprosy is treated for 12 months.
MDT is provided free of charge by the World Health Organization (WHO) in many countries.
Early diagnosis and treatment are essential to prevent disability and nerve damage.

Complications:

If left untreated, leprosy can lead to severe and permanent complications, including:

Permanent nerve damage, resulting in loss of sensation and muscle weakness/paralysis in the hands and feet.
Disfigurement of the face, hands, and feet.
Blindness.
Kidney failure.
Erectile dysfunction in men.

Prevention:

Early detection and treatment of infected individuals are key to preventing the spread of leprosy.
Contact tracing is important to identify and monitor individuals who have been in close contact with infected persons.
Chemoprophylaxis with a single dose of rifampicin (SDR) is recommended for contacts of leprosy patients in some regions. However, its widespread use is still under debate.

Stigma:

Historically, leprosy has been associated with significant stigma and social isolation. This stigma can prevent individuals from seeking treatment and can have a devastating impact on their lives. Education and awareness campaigns are crucial to reducing stigma and promoting early diagnosis and treatment.

Global Situation:

Leprosy is still a public health problem in some parts of the world, particularly in Southeast Asia, Africa, and South America. However, global efforts to control leprosy have been very successful, and the number of new cases has declined significantly in recent decades. The goal is to eliminate leprosy as a public health problem worldwide.

In summary, leprosy (Hansen's disease) is a treatable infectious disease that primarily affects the skin and nerves. Early diagnosis and treatment are crucial to prevent complications and disability. While still present in certain regions, global efforts have significantly reduced its prevalence. Combating the stigma associated with the disease remains important.