Module 17: Leprosy (Hansen's Disease)

1. Learning Outcomes

By the end of this session, students should be able to:

• Explain the pathogenesis, transmission, and classification of leprosy.

• Identify clinical features and complications, and outline diagnostic approaches.

• Discuss prevention strategies and current WHO-recommended treatment protocols.

2. Introduction & Prevalence

• Leprosy is a chronic infectious disease caused by Mycobacterium leprae.

• Affects skin, peripheral nerves, eyes, and upper respiratory mucosa.

• Transmission: Prolonged close contact via nasal droplets from untreated patients.

• Global burden: ~200,000 new cases annually; endemic in India, Brazil, Indonesia.

• Malaysia: 66 new cases reported by May 2025; outbreaks in Negeri Sembilan and Sabah.

3. Aetiology

• Caused by Mycobacterium leprae, an acid-fast bacillus.

• Incubation period: 5–20 years.

• Cannot be cultured in vitro; diagnosis is clinical and histopathological.

• Transmission requires prolonged exposure; it is not spread by casual contact.

4. Diagnosis

Clinical Features

• Skin lesions: Hypopigmented or erythematous patches with sensory loss.

• Peripheral nerve involvement: Thickened nerves, muscle weakness, paresthesia.

• Ocular signs: Lagophthalmos, corneal ulcers, blindness.

• Other signs: Madarosis, nasal collapse, claw hand.

Cardinal Signs (WHO)

• Definite sensory loss in skin patch.

• Thickened/enlarged peripheral nerve with sensory/motor loss.

• Presence of bacilli in slit-skin smear.

Classification

• Paucibacillary (PB): ≤5 lesions, no bacilli.

• Multibacillary (MB): >5 lesions, bacilli present or nerve involvement.

Diagnosis confirmed by one of:

• Skin Slit Smear: Dermis smear checked for acid-fast bacilli; for multibacillary leprosy.

• Lepromin Test: Intradermal test to classify leprosy type.

• Skin Biopsy: Shows leprosy features; may need special stains.

• M. leprae DNA PCR: Highly specific for leprosy detection.

Images

Fig. 17.1: M. leprae acid-fast bacilli (Ziehl–Neelsen stain)

As an acid-fast bacterium, M. leprae appears red when a Ziehl–Neelsen stain is used.

Fig. 17.2: Leprosy — Tuberculoid (well-defined erythematous plaque on the cheek)

Image sourced from DermNet.

Paucibacillary form is defined clinically by:

• A few (1–2) sharply defined red patches with raised borders or a single larger hypopigmented patch less than 10 cm in diameter

• Loss of sweating with rough, dry hairless skin in the patches

• Loss of sensation in lesions

• Affected nerves are thickened and tender on palpation

Fig. 17.3: Lepromatous leprosy (i), (ii), (iii)

Image sourced from DermNet.

Multibacillary form is defined by:

• Early symptoms: nasal stuffiness, discharge, and bleeding

• Swelling and thickening of limbs

• Widespread poorly defined hypopigmented and erythematous macules; shiny surface, sensation may be normal

• Progresses to infiltration of skin (nodules and plaques)

• Characteristic leonine facies with thickening of the forehead, loss of eyebrows and eyelashes (madarosis), distortion of the nose, and thickening of the earlobes

• Involvement of other systems

Table 17.1: Differential Diagnosis of Hypopigmented Patches and Macules

Differential Diagnosis	Clinical Features	Key Distinguishing Points	Diagnostic Tests/Clues
Pityriasis alba	Hypopigmented, ill-defined scaly patches	Mostly in children, no sensory loss	Clinical appearance
Pityriasis versicolor	Hypo/hyperpigmented fine scaling patches	Caused by Malassezia yeast	KOH preparation showing yeast hyphae
Leishmaniasis	Ulcerative or plaque lesions	History of sandfly exposure	Skin biopsy, smear to identify parasites
Yaws	Papillomatous or ulcerative lesions in children	Tropical endemic area	Serology tests
Cutaneous leishmaniasis	Chronic ulcer/plaque, raised borders	Endemic region, raised lesion borders	Parasite demonstration in biopsy/smear
Lupus vulgaris (cutaneous tuberculosis)	Slowly progressive plaques, apple jelly nodules on diascopy	Positive tuberculin skin test	Skin biopsy showing caseating granulomas
Leprosy	Hypopigmented or erythematous patches, loss of sensation, thickened nerves	Peripheral nerve thickening, sensory/motor deficits, chronic onset	Acid-fast bacilli in skin smears/biopsy, clinical nerve exam
Fungal infections (e.g., tinea corporis)	Scaly plaques	No nerve involvement	KOH prep, fungal culture
Vitiligo	Depigmented well-demarcated patches	No sensory loss	Clinical appearance
Sarcoidosis	Papules or plaques	Non-caseating granulomas on biopsy	Skin biopsy histology

5. Complications

Neurological

• Peripheral neuropathy → claw hand, foot drop.

• Nerve abscesses.

Ocular

• Corneal ulcers, uveitis, blindness.

Skin

• Chronic ulcers, secondary infections.

Systemic

Lepra reactions:

• Type 1 (Reversal): Inflammation of existing lesions, neuritis.

• Type 2 (ENL): Painful nodules, fever, systemic symptoms.

Psychosocial

• Stigma, discrimination, depression.

6. Prevention & Treatment

Prevention

• Early detection and MDT.

• Contact tracing and Single Dose Rifampicin (SDR-PEP) for contacts.

• BCG vaccine offers partial protection.

• Community education to reduce stigma.

Treatment (WHO MDT Guidelines 2025)

• PB Leprosy:

  • Duration: 6 months.

  • Drugs: Rifampicin (monthly) + Dapsone (daily).

• MB Leprosy:

  • Duration: 12 months.

  • Drugs: Rifampicin (monthly) + Dapsone (daily) + Clofazimine (daily + monthly).

• MDT is free via WHO and MOH Malaysia.

• Lepra reactions:

  • Type 1: Prednisolone.

  • Type 2: Thalidomide (if available), corticosteroids.

7. Expanded Treatment for Leprosy

MDT is the standard treatment for all forms of leprosy. It prevents drug resistance, ensures cure, and reduces transmission. It is supplied free of charge by WHO to endemic countries including Malaysia.

Fig. 17.4: WHO MDT blister pack for leprosy

Paucibacillary (PB) Leprosy

Definition: ≤5 skin lesions, no bacilli on slit-skin smear.

Duration: 6 months

Drug Regimen:

• Rifampicin: 600 mg once monthly (supervised)

• Dapsone: 100 mg daily (self-administered)

• Clofazimine: 50 mg daily + 300 mg once monthly (added in 2025 update)

Notes:

• Rifampicin may cause reddish urine temporarily.

• Clofazimine may cause skin discoloration and dryness.

• Dapsone is generally safe; monitor for sulfa allergy.

Multibacillary (MB) Leprosy

Definition: >5 skin lesions, bacilli present, or nerve involvement.

Duration: 12 months

Drug Regimen:

• Rifampicin: 600 mg once monthly (supervised)

• Dapsone: 100 mg daily (self-administered)

• Clofazimine: 50 mg daily + 300 mg once monthly (self-administered + supervised)

Notes:

• MDT is highly effective in killing M. leprae.

• Adherence is crucial to prevent relapse and resistance.

• MDT is available at all MOH facilities in Malaysia.

Management of Lepra Reactions

Table 17.2: Management of Lepra Reactions

Reaction	Type	Symptoms	Treatment
Type 1 (Reversal Reaction)	Occurs in borderline forms	Inflammation of existing lesions, neuritis	Prednisolone 40–60 mg/day tapered over weeks; continue MDT
Type 2 (ENL — Erythema Nodosum Leprosum)	Occurs in MB cases	Painful nodules, fever, systemic symptoms	Thalidomide 100–300 mg/day (if available); Prednisolone or Clofazimine (anti-inflammatory dose); supportive care

Monitoring and Follow-Up

• Monthly supervised doses.

• Monitor for:

  • Drug side effects (rash, GI upset, pigmentation).

  • Nerve function (sensory/motor).

  • Signs of lepra reactions.

• Post-treatment disability care and rehabilitation.

Multiple Choice Questions

Tap an answer to check yourself — the correct option and an explanation appear once you choose.

Q1 A 35-year-old rubber tapper from Kuala Pilah presents with numb hypopigmented patches on his arms and a thickened ulnar nerve. Slit-skin smear is negative. What is the most likely classification?

• A Multibacillary leprosy
• B Paucibacillary leprosy
• C Tuberculoid leprosy
• D Indeterminate leprosy

Q2 A 42-year-old man on MDT for MB leprosy develops painful nodules, fever, and joint pain. What is the most likely diagnosis?

• A Type 1 lepra reaction
• B Type 2 lepra reaction (ENL)
• C Drug allergy
• D Secondary bacterial infection

Q3 Which of the following drugs used in MDT causes skin discoloration?

• A Rifampicin
• B Dapsone
• C Clofazimine
• D Isoniazid

Short Answer Questions (SAQs)

SAQ 1: Cardinal Signs and Treatment of Paucibacillary Leprosy

SAQ

A 28-year-old woman presents with a single hypopigmented patch on her thigh with sensory loss. There is no nerve thickening.

a) What are the cardinal signs of leprosy (WHO)?

b) What is the recommended treatment for this patient?

Reveal model answer

Model answer

a) Cardinal signs of leprosy (WHO):

1. Definite sensory loss in a skin patch.
2. Thickened or enlarged peripheral nerve with associated sensory or motor loss.
3. Presence of acid-fast bacilli in slit-skin smear.

One cardinal sign is sufficient to diagnose leprosy.

b) Treatment:

This patient has a single hypopigmented patch with sensory loss and a negative nerve examination — consistent with Paucibacillary (PB) leprosy (≤5 lesions, no bacilli).

Recommended regimen:

• Rifampicin 600 mg once monthly (supervised)
• Dapsone 100 mg daily (self-administered)
• Duration: 6 months

MDT is available free of charge at all MOH facilities in Malaysia. Counsel the patient on medication side effects (reddish urine from Rifampicin) and the importance of adherence to prevent relapse.

SAQ 2: Complications and Management of Advanced Leprosy

SAQ

A 50-year-old man with multibacillary leprosy develops claw hand and foot drop.

a) What complications of leprosy have occurred in this patient?

b) How would you manage this patient?

Reveal model answer

Model answer

a) Complications:

• Peripheral neuropathy — damage to ulnar and common peroneal nerves leads to claw hand and foot drop respectively.
• Deformity and disability — progressive without treatment.
• This patient is also at risk of ocular complications (lagophthalmos, corneal ulcers), chronic skin ulcers, and secondary infections.
• Psychosocial complications: stigma, depression, and social discrimination are significant burdens in leprosy.

b) Management:

• Continue MDT — MB regimen (Rifampicin + Dapsone + Clofazimine for 12 months); MDT kills M. leprae and prevents further nerve damage.
• Monitor for lepra reactions — particularly Type 1 (reversal) which causes additional neuritis; treat with Prednisolone if present.
• Nerve function assessment — regular sensory and motor testing to detect new nerve damage early.
• Physiotherapy — to maintain joint mobility and prevent further contracture.
• Orthotic support — splints and footwear adaptations for foot drop and claw hand.
• Surgical referral — if reconstructive or tendon-transfer surgery is appropriate.
• Post-treatment disability care and rehabilitation — coordinate with physiotherapy and occupational therapy.
• Psychosocial support — address stigma, counsel patient and family, and facilitate community re-integration.

OSCE Stations

OSCE 1: Evaluation and Counselling of Suspected Leprosy

OSCE

Scenario: A 40-year-old plantation worker presents with numb skin patches and thickened nerves on examination.

Task: Take a focused history, examine the patient, and counsel on diagnosis, treatment, stigma, and contact tracing.

Self-assess against checklist

Tick each point you covered, then check your score.

• Asks about onset and duration of skin patches and numbness.
• Enquires about history of close contact with a known leprosy case.
• Asks about other symptoms: nasal discharge, eye changes, limb weakness.
• Examines skin lesions: number, distribution, hypopigmentation or erythema.
• Tests sensation in skin patches (light touch, pin-prick).
• Palpates peripheral nerves for thickening and tenderness (e.g., ulnar, common peroneal).
• Assesses for motor deficits: claw hand, foot drop.
• Explains the diagnosis clearly and addresses stigma: leprosy is curable with MDT.
• Outlines the MDT regimen appropriate to classification (PB 6 months or MB 12 months).
• Counsels on medication side effects (reddish urine from Rifampicin, skin darkening from Clofazimine).
• Advises that MDT is free at all MOH facilities.
• Discusses contact screening and SDR-PEP for close contacts.
• Emphasises adherence to prevent relapse and resistance.
• Provides psychosocial reassurance and addresses community stigma.