Leprosy (Hansen’s Disease) – A Comprehensive Medical Guide

Overview

Leprosy, also called Hansen’s disease, is a chronic infectious disease caused by the bacterium Mycobacterium leprae. It primarily affects the skin, peripheral nerves, mucous membranes of the upper respiratory tract, and the eyes. The disease has a long incubation period—typically 5 – 7 years, but it can range from 2 to 20 years—making early detection challenging.

Who it affects: Leprosy can affect anyone, regardless of age, sex, or ethnicity, but the highest burden is seen in regions with limited access to health care and crowded living conditions. Historically, the disease was more common among men, but transmission patterns are now considered gender‑neutral.

Global prevalence: According to the World Health Organization (WHO), there were **202,256 new cases reported worldwide in 2023**, a modest decline from previous years but still indicating endemic transmission in certain areas. Over 90 % of cases are reported from just **six countries**: India, Brazil, Indonesia, Bangladesh, Nigeria, and the Democratic Republic of Congo.^{WHO 2024} In the United States, leprosy is rare, with **≈200–300 new cases reported each year**, most of which are linked to travel or immigration from endemic regions.^CDC

Symptoms

Leprosy presents along a spectrum—from tuberculoid (paucibacillary) to lepromatous (multibacillary)—based on the host’s immune response. Symptoms may appear slowly and can be subtle.

Skin manifestations

• Hypopigmented or reddish patches—areas with loss of sensation, often dry and hairless.
• Raised nodules or plaques—more common in lepromatous disease.
• Thickened dermis—giving a “leonine facies” (lion‑like appearance) in advanced cases.
• Ulceration—secondary infection can occur in anesthetic areas.

Neurologic signs

• Loss of sensation—especially to light touch, temperature, and pain in affected skin patches.
• Peripheral nerve thickening—palpable nodules over peripheral nerves (e.g., ulnar, peroneal).
• Motor weakness—hand grip weakness, foot drop, or facial muscle weakness.
• Sensory loss in extremities—leading to repeated injuries, burns, or new ulcers.

Ocular involvement

• Dry eyes, corneal ulceration, and vision loss due to bacterial infiltration of the trigeminal nerve.

Other systemic signs

• Enlarged nerves (e.g., ulnar, median, posterior tibial) detectable on physical exam.
• Testicular atrophy in men (due to involvement of the genital nerves).
• Recurrent nasal congestion or epistaxis from mucosal involvement.

Symptoms develop gradually, often over months to years. Early detection is crucial because nerve damage can become permanent if treatment is delayed.

Causes and Risk Factors

Cause

Leprosy is caused by Mycobacterium leprae, an intracellular, acid‑fast bacillus that prefers cool temperatures (32‑36 °C), explaining its predilection for skin and superficial nerves.

Transmission

• Respiratory droplets—the most widely accepted route; prolonged close contact with an untreated, infectious individual increases risk.
• Skin-to-skin contact—possible but less common.
• Animal reservoirs—certain armadillo species in the southern United States carry a strain of M. leprae; handling or consuming undercooked armadillo meat is a documented risk.^{NEJM 2015}

Risk factors

• Living in or traveling to endemic areas.
• Close, prolonged contact with untreated patients.
• Genetic susceptibility—certain HLA types and innate immune defects.
• Compromised cellular immunity (e.g., HIV co‑infection, malnutrition).
• Occupations that involve frequent contact with armadillos (e.g., wildlife researchers).

Diagnosis

Because leprosy mimics many dermatologic and neurologic conditions, a combination of clinical evaluation and laboratory testing is required.

Clinical assessment

• Detailed skin examination for characteristic patches, nodules, or plaques.
• Neurologic testing for loss of sensation using a monofilament (10 g Semmes–Weinstein) and assessment of nerve thickening.
• Slit‑skin smear (SSS) from multiple sites to detect acid‑fast bacilli (AFB).

Laboratory tests

• Skin biopsy—histopathology shows granulomatous inflammation; Ziehl‑Neelsen staining can reveal AFB.
• Polymerase chain reaction (PCR)—detects M. leprae DNA; useful when smear is negative.
• Serologic tests (e.g., anti‑PGL‑1 antibody) can support diagnosis but are not definitive.

Classification

After diagnosis, patients are classified to guide therapy:

• Paucibacillary (PB) – ≤5 skin lesions, negative SSS.
• Multibacillary (MB) – >5 lesions or positive SSS.

Treatment Options

The WHO recommends multidrug therapy (MDT) that cures >95 % of patients and prevents resistance.

Standard MDT regimens

Classification	Drugs (monthly)	Duration
Paucibacillary (PB)	Rifampicin 600 mg + Dapsone 100 mg (both given under direct observation)	6 months
Multibacillary (MB)	Rifampicin 600 mg + Dapsone 100 mg + Clofazimine 300 mg	12 months

All drugs are administered once a month under supervision, with daily self‑administered dapsone (and clofazimine for MB) at home.

Adjunctive therapies

• Prednisone or other corticosteroids for acute neuritis (nerve inflammation).
• Thalidomide for painful erythema nodosum leprosum (ENL) reactions—used with caution due to teratogenicity.
• Physical therapy and orthotics to preserve function.

Monitoring and side‑effects

• Rifampicin – hepatotoxicity, orange body fluids; monitor liver enzymes.
• Dapsone – hemolysis in G6PD‑deficient patients, methemoglobinemia; baseline G6PD testing recommended.
• Clofazimine – skin discoloration (brown‑black), gastrointestinal upset.

Lifestyle and supportive care

• Good nutrition to support immune recovery.
• Avoiding alcohol and hepatotoxic drugs while on rifampicin.
• Regular skin care to prevent secondary infections.

Living with Leprosy (Hansen’s Disease)

With effective MDT, most patients lead normal lives, but ongoing management is essential to prevent disability.

Daily management tips

1. Skin protection: Check anesthetic areas daily for injuries, burns, or ulcers; use soft footwear and avoid extreme temperatures.
2. Neuropathy care: Perform self‑exams of hand and foot sensation weekly; report new numbness promptly.
3. Eye hygiene: Use lubricating eye drops if corneal dryness occurs; protect eyes with sunglasses.
4. Medication adherence: Keep a medication diary; set reminders for monthly supervised doses.
5. Physical therapy: Engage in exercises prescribed by a physiotherapist to maintain muscle strength and joint mobility.
6. Psychosocial support: Join support groups (e.g., The Leprosy Mission) to combat stigma and depression.

Social considerations

Stigma remains a barrier in many endemic regions. Education of families, schools, and coworkers can reduce discrimination. In most high‑income countries, patients have legal protection against employment discrimination.

Prevention

• Early detection & treatment of infected individuals reduces transmission; World Health Organization recommends contact tracing and prophylactic single‑dose rifampicin (SDR) for close contacts.
• Vaccination – The BCG vaccine offers partial protection (≈20‑40 %); it is part of routine infant immunization in many endemic countries.
• Personal protective measures – Avoid prolonged close contact with untreated cases and practice hand hygiene.
• Animal exposure – In the U.S., avoid handling or consuming undercooked armadillos.

Complications

If left untreated or inadequately treated, leprosy can cause irreversible damage.

• Peripheral neuropathy leading to loss of sensation, repeated injuries, and chronic ulcers.
• Disfiguring skin lesions (leonine facies, nasal collapse) that cause social stigma.
• Eye complications – corneal ulceration, cataracts, and blindness.
• ENL (type 2 reaction) – painful nodules, fever, and organ involvement; may be life‑threatening if not treated.
• Secondary infections of ulcers, potentially leading to osteomyelitis.
• Cardiopulmonary involvement – rare but reported in advanced multibacillary disease.

When to Seek Emergency Care

References

1. World Health Organization. Leprosy Fact Sheet. Updated 2024.
2. Centers for Disease Control and Prevention. Leprosy (Hansen Disease) – CDC. Accessed June 2026.
3. Mayo Clinic. Leprosy: Symptoms and Causes.
4. Cleveland Clinic. Leprosy (Hansen’s Disease).
5. Shetty, S. et al. “Armadillos as a source of Mycobacterium leprae infection in the United States.” New England Journal of Medicine, 2015; 372:1007‑1015.
6. World Health Organization. “Guidelines for the diagnosis, treatment and prevention of leprosy.” WHO Technical Report Series, No. 1013, 2023.