Leprosy, also known as Hansen's disease, is a long-term infectious condition caused by the bacterium Mycobacterium leprae. This disease mainly affects the skin, peripheral nerves, eyes, and the lining of the nose. While it is a serious illness, leprosy is curable and not highly contagious. Prompt diagnosis and treatment are key to preventing permanent disability and limiting transmission.

Globally, over 200,000 new cases of leprosy are diagnosed each year. In the United States, it remains rare, with approximately 150 to 250 new cases annually. Most people exposed to the bacterium do not develop symptoms due to natural immunity.

Types of Leprosy

Leprosy can be classified based on immune response and bacterial load or using the simplified WHO system.

Traditional Classification:

  • Tuberculoid leprosy: Characterized by a strong immune response and limited bacterial presence. It causes well-defined skin lesions and localized nerve involvement.

  • Borderline leprosy: This form has a moderate immune response with more widespread skin and nerve damage.

  • Lepromatous leprosy: The most severe form, marked by a weak immune response, numerous skin lesions, and extensive nerve involvement.

WHO Classification:

  • Paucibacillary (PB) leprosy: Defined by five or fewer skin lesions and minimal nerve involvement.

  • Multibacillary (MB) leprosy: Involves six or more lesions and multiple affected nerves.

This classification system determines the treatment approach and expected outcomes.

Key Symptoms

Leprosy develops slowly, often taking 5–7 years after exposure to present symptoms. In some cases, it can take up to 20 years. It primarily targets the skin and peripheral nerves.

Skin-Related Symptoms:

  • Pale or reddish patches

  • Numbness in affected skin

  • Thickened, dry, or rough skin

  • Painless ulcers on feet

  • Swelling on the face or ears

  • Loss of eyebrows or eyelashes

Nerve-Related Symptoms:

  • Tingling or numbness in extremities

  • Weakness in hands or feet

  • Deformities such as claw fingers or foot drop

  • Loss of sensation and reflexes

  • Eye issues such as dryness or vision loss

Nasal Symptoms:

  • Persistent nasal congestion

  • Frequent nosebleeds

  • Collapse or disfigurement of the nose

Early symptoms are often painless, which delays diagnosis in many cases.

Main Causes

Leprosy is caused by the slow-growing Mycobacterium leprae. This bacterium spreads through respiratory droplets (via coughing or sneezing) from untreated individuals. Prolonged and close exposure is usually necessary for transmission.

Once inside the body, the bacteria invade skin cells and peripheral nerves, replicating slowly. The host's immune response largely determines the severity and spread of the disease.

Fortunately, about 95% of people have natural resistance and do not develop leprosy, even after exposure.

Risk Factors

Most people are naturally immune to leprosy, but several factors can increase susceptibility:

  • Close contact with untreated patients

  • Weakened immune system (e.g., HIV, cancer, diabetes)

  • Living in or traveling to endemic areas: such as Brazil, India, Indonesia, Ethiopia, and Nepal

  • Genetic predisposition

  • Handling armadillos: These animals are natural reservoirs of M. leprae in some regions

Understanding these risk factors can help guide early screening and preventive measures.

Diagnosis

Diagnosing leprosy involves a combination of clinical assessment and laboratory testing:

1. Physical Examination: Healthcare providers look for visible skin lesions and signs of nerve damage such as loss of sensation or muscle weakness.

2. Skin Smear: A small sample of tissue fluid is collected and stained for the presence of M. leprae under a microscope.

3. Skin Biopsy: A tissue sample is examined to confirm bacterial presence and assess disease classification.

4. Lepromin Skin Test (optional): This test helps classify the form of leprosy but is not used for diagnosis.

Imaging or nerve conduction studies may also be used in complex cases.

Available Treatments

Leprosy is treatable and curable through a standard protocol called Multi-Drug Therapy (MDT), recommended by the World Health Organization.

Medications in MDT include:

  • Rifampicin

  • Clofazimine

  • Dapsone

Treatment duration:

  • PB Leprosy: 6–12 months

  • MB Leprosy: Up to 24 months

Supportive Therapies:

  • Pain relief (e.g., gabapentin for nerve pain)

  • Wound care for ulcers or infected lesions

  • Eye care for patients with ocular involvement

  • Physical therapy or orthopedic devices for deformity prevention and rehabilitation

The treatment is available free of charge globally via WHO initiatives.

Prevention

Though not highly contagious, prevention is essential for public health:

Effective strategies include:

  • Early diagnosis and treatment: The best way to prevent spread

  • Avoid close, frequent contact with untreated individuals

  • Post-exposure prophylaxis: A single dose of rifampicin can reduce infection risk in contacts

  • Avoid handling wild armadillos in areas where they are known carriers

  • Routine health checks in endemic areas

Public health education and destigmatization are also critical in early detection.

Potential Complications

If untreated, leprosy can lead to serious health consequences, including:

  • Permanent nerve damage

  • Blindness

  • Muscle weakness or paralysis

  • Chronic ulcers

  • Loss of fingers or toes

  • Facial disfigurement (e.g., collapsed nose)

  • Erectile dysfunction and infertility

  • Kidney damage in rare cases

Even after completing treatment, some people may require long-term care for irreversible damage.

Living With Leprosy

With early treatment, the prognosis for leprosy is excellent. Most people recover fully without complications. For those with more severe or delayed cases, supportive care can help manage symptoms and improve quality of life.

Recovery tips include:

  • Adhering to medication schedule

  • Attending regular follow-up visits

  • Using protective footwear and gloves for areas with numbness

  • Engaging in physical therapy to maintain mobility

  • Joining support groups for emotional and mental health

Combating stigma remains essential for patient well-being and reintegration into society.