MBBS Year
2nd Year
Subject
What Is Usually Asked
Properties of M. leprae, laboratory diagnosis, lepromin test
ReferenceAll Years (1st-Final)All UniversitiesLeprosy
Leprosy: Notes, PPT and PYQs for MBBS
Leprosy (Hansen's disease) is a chronic infectious disease caused by Mycobacterium leprae that mainly affects the skin and peripheral nerves. Early diagnosis and multidrug therapy cure the infection and prevent disability. Leprosy is examined in Microbiology, Pathology and Pharmacology in 2nd Year, Community Medicine in 3rd Year, and General Medicine (including dermatology) in Final Year.
SME-reviewed. Updated 2026.
Open in GeckoMed for PPT slides and notes.Quick Summary: What You Need to Know for University Exams
- The cause is Mycobacterium leprae, an acid-fast, obligate intracellular bacillus that cannot be grown in artificial culture media.
- It affects the skin and peripheral nerves, especially in cooler parts of the body.
- Diagnosis rests on WHO cardinal signs: an anaesthetic skin patch, a thickened peripheral nerve with sensory or motor loss, or a positive slit-skin smear.
- The Ridley-Jopling classification places cases on a spectrum from tuberculoid (strong immunity) to lepromatous (weak immunity).
- For treatment, cases are grouped as paucibacillary (PB) or multibacillary (MB).
- Since 1 April 2025, India uses a three-drug MDT (rifampicin, dapsone and clofazimine) for both PB and MB leprosy.
- Lepra reactions are important causes of nerve damage and need prompt treatment.
Leprosy Across MBBS Subjects
| MBBS Year | Subject | What Is Usually Asked |
|---|---|---|
| 2nd Year | Microbiology | Properties of M. leprae, laboratory diagnosis, lepromin test |
| 2nd Year | Pathology | Tuberculoid versus lepromatous leprosy, granuloma, lepra cells |
| 2nd Year | Pharmacology | Antileprosy drugs and adverse effects |
| 3rd Year | Community Medicine | Epidemiology, classification for treatment, national programme |
| Final Year | General Medicine | Clinical features, nerve involvement, reactions, management |
MBBS Year
2nd Year
Subject
What Is Usually Asked
Tuberculoid versus lepromatous leprosy, granuloma, lepra cells
MBBS Year
2nd Year
Subject
What Is Usually Asked
Antileprosy drugs and adverse effects
MBBS Year
3rd Year
Subject
What Is Usually Asked
Epidemiology, classification for treatment, national programme
MBBS Year
Final Year
Subject
What Is Usually Asked
Clinical features, nerve involvement, reactions, management
Definition and Classification
Definition: Leprosy is a chronic granulomatous infection caused by Mycobacterium leprae, mainly affecting the skin, peripheral nerves, mucosa of the upper respiratory tract and eyes.
WHO Cardinal Signs
A case of leprosy has at least one of the following:
- Definite loss of sensation in a pale (hypopigmented) or reddish skin patch
- A thickened or enlarged peripheral nerve with loss of sensation and/or weakness of the muscles it supplies
- Acid-fast bacilli in a slit-skin smear
Ridley-Jopling Classification (Immunological Spectrum)
| Type | Immunity | Bacilli | Key Features |
|---|---|---|---|
| Tuberculoid (TT) | Strong cell-mediated immunity | Very few or none | Few well-defined anaesthetic patches; early nerve involvement |
| Borderline tuberculoid (BT) | Fairly strong | Few | Several patches; asymmetrical nerve thickening |
| Mid-borderline (BB) | Unstable | Moderate | Many lesions, "punched-out" appearance; unstable |
| Borderline lepromatous (BL) | Weak | Many | Many lesions, widespread nerve involvement |
| Lepromatous (LL) | Very weak | Very many | Symmetrical, diffuse infiltration, nodules, leonine facies, loss of eyebrows |
| Indeterminate | Undetermined | Few | Early single hypopigmented patch |
Type
Tuberculoid (TT)
Immunity
Strong cell-mediated immunity
Bacilli
Very few or none
Key Features
Few well-defined anaesthetic patches; early nerve involvement
Type
Borderline tuberculoid (BT)
Immunity
Fairly strong
Bacilli
Few
Key Features
Several patches; asymmetrical nerve thickening
Type
Mid-borderline (BB)
Immunity
Unstable
Bacilli
Moderate
Key Features
Many lesions, "punched-out" appearance; unstable
Type
Borderline lepromatous (BL)
Immunity
Weak
Bacilli
Many
Key Features
Many lesions, widespread nerve involvement
Type
Lepromatous (LL)
Immunity
Very weak
Bacilli
Very many
Key Features
Symmetrical, diffuse infiltration, nodules, leonine facies, loss of eyebrows
Type
Indeterminate
Immunity
Undetermined
Bacilli
Few
Key Features
Early single hypopigmented patch
Classification for Treatment
| Group | Features |
|---|---|
| Paucibacillary (PB) | 1 to 5 skin lesions, without demonstrated bacilli in a skin smear |
| Multibacillary (MB) | More than 5 skin lesions, or nerve involvement, or positive slit-skin smear irrespective of the number of lesions |
Group
Paucibacillary (PB)
Features
1 to 5 skin lesions, without demonstrated bacilli in a skin smear
Group
Multibacillary (MB)
Features
More than 5 skin lesions, or nerve involvement, or positive slit-skin smear irrespective of the number of lesions
Aetiology
The Organism
| Property | Details |
|---|---|
| Staining | Acid-fast, but decolourised more easily than M. tuberculosis (a weaker acid is used in Ziehl-Neelsen staining for M. leprae) |
| Growth | Obligate intracellular; cannot be grown in artificial culture media |
| Experimental hosts | Mouse footpad and the nine-banded armadillo |
| Generation time | Very slow, about 12 to 14 days |
| Preferred sites | Schwann cells of peripheral nerves and macrophages; cooler parts of the body |
| Arrangement in LL | Bacilli in clumps called globi |
Property
Staining
Details
Acid-fast, but decolourised more easily than M. tuberculosis (a weaker acid is used in Ziehl-Neelsen staining for M. leprae)
Property
Growth
Details
Obligate intracellular; cannot be grown in artificial culture media
Property
Experimental hosts
Details
Mouse footpad and the nine-banded armadillo
Property
Generation time
Details
Very slow, about 12 to 14 days
Property
Preferred sites
Details
Schwann cells of peripheral nerves and macrophages; cooler parts of the body
Property
Arrangement in LL
Details
Bacilli in clumps called globi
Transmission and Risk Factors
- Mainly through droplets from the nose and mouth of untreated patients, usually multibacillary
- Needs prolonged close contact
- Long incubation period, often several years
- Risk factors: household contact with an untreated patient, poverty, overcrowding and genetic susceptibility
Pathophysiology
Flowchart
- M. leprae enters through the respiratory tract and reaches skin and nerves
- It infects macrophages and Schwann cells
- The host's cell-mediated immunity determines the type of disease
- Strong Th1 response: well-formed granulomas and few bacilli (tuberculoid pole)
- Weak Th1 response with a Th2 bias: poorly organised infiltrates with foamy macrophages full of bacilli (lepromatous pole)
- Nerve damage from infection and inflammation causes sensory loss, then muscle weakness and deformity
Pathology
| Feature | Tuberculoid | Lepromatous |
|---|---|---|
| Granulomas | Well-formed epithelioid granulomas with lymphocytes | Poorly formed; sheets of foamy macrophages (lepra cells or Virchow cells) |
| Grenz zone | Absent (granulomas reach the epidermis) | Present (clear band below the epidermis) |
| Bacilli | Rare | Abundant, often in globi |
| Nerves | Destroyed early by granulomas | Infiltrated by bacilli |
Feature
Granulomas
Tuberculoid
Well-formed epithelioid granulomas with lymphocytes
Lepromatous
Poorly formed; sheets of foamy macrophages (lepra cells or Virchow cells)
Feature
Grenz zone
Tuberculoid
Absent (granulomas reach the epidermis)
Lepromatous
Present (clear band below the epidermis)
Feature
Bacilli
Tuberculoid
Rare
Lepromatous
Abundant, often in globi
Feature
Nerves
Tuberculoid
Destroyed early by granulomas
Lepromatous
Infiltrated by bacilli
(Examiner may ask you to compare tuberculoid and lepromatous leprosy in a table.)
Clinical Features
Skin
- Hypopigmented or reddish patches with loss of sensation (touch, temperature, pain), reduced sweating and hair loss
- In lepromatous leprosy: diffuse infiltration, nodules, thickened ear lobes, loss of the outer eyebrows (madarosis) and leonine facies
Nerves
| Commonly Thickened Nerve | Resulting Deformity |
|---|---|
| Ulnar nerve (most commonly affected) | Claw hand |
| Median nerve | Ape thumb deformity |
| Radial nerve | Wrist drop |
| Common peroneal (lateral popliteal) nerve | Foot drop |
| Posterior tibial nerve | Anaesthetic sole, plantar ulcers, clawed toes |
| Facial nerve | Lagophthalmos (inability to close the eye) |
| Great auricular nerve | Visibly thickened in the neck |
Commonly Thickened Nerve
Ulnar nerve (most commonly affected)
Resulting Deformity
Claw hand
Commonly Thickened Nerve
Median nerve
Resulting Deformity
Ape thumb deformity
Commonly Thickened Nerve
Radial nerve
Resulting Deformity
Wrist drop
Commonly Thickened Nerve
Common peroneal (lateral popliteal) nerve
Resulting Deformity
Foot drop
Commonly Thickened Nerve
Posterior tibial nerve
Resulting Deformity
Anaesthetic sole, plantar ulcers, clawed toes
Commonly Thickened Nerve
Facial nerve
Resulting Deformity
Lagophthalmos (inability to close the eye)
Commonly Thickened Nerve
Great auricular nerve
Resulting Deformity
Visibly thickened in the neck
Other Features
- Eyes: lagophthalmos, corneal anaesthesia and ulcers, iridocyclitis
- Nose: nasal stuffiness, bleeding and collapse (saddle nose) in lepromatous disease
- Testes: atrophy and gynaecomastia in lepromatous disease
Lepra Reactions
| Feature | Type 1 Reaction (Reversal Reaction) | Type 2 Reaction (Erythema Nodosum Leprosum) |
|---|---|---|
| Mechanism | Cell-mediated (delayed hypersensitivity) | Immune complex-mediated |
| Seen in | Borderline leprosy (BT, BB, BL) | BL and LL |
| Features | Existing lesions become red, swollen and tender; painful neuritis | Crops of tender red nodules, fever, neuritis, iritis, orchitis, joint pain |
| Treatment | Corticosteroids | Corticosteroids; thalidomide (not in women who may become pregnant); clofazimine |
Feature
Mechanism
Type 1 Reaction (Reversal Reaction)
Cell-mediated (delayed hypersensitivity)
Type 2 Reaction (Erythema Nodosum Leprosum)
Immune complex-mediated
Feature
Seen in
Type 1 Reaction (Reversal Reaction)
Borderline leprosy (BT, BB, BL)
Type 2 Reaction (Erythema Nodosum Leprosum)
BL and LL
Feature
Features
Type 1 Reaction (Reversal Reaction)
Existing lesions become red, swollen and tender; painful neuritis
Type 2 Reaction (Erythema Nodosum Leprosum)
Crops of tender red nodules, fever, neuritis, iritis, orchitis, joint pain
Feature
Treatment
Type 1 Reaction (Reversal Reaction)
Corticosteroids
Type 2 Reaction (Erythema Nodosum Leprosum)
Corticosteroids; thalidomide (not in women who may become pregnant); clofazimine
Lepra reactions are medical emergencies for the nerves. Untreated neuritis can cause permanent paralysis within days.
Diagnosis
| Test | Purpose |
|---|---|
| Clinical examination | Skin patches, sensory testing, palpation of peripheral nerves |
| Slit-skin smear | Detects acid-fast bacilli; the bacteriological index (BI) measures bacterial load on a 0 to 6+ scale, and the morphological index (MI) estimates the proportion of live, solidly staining bacilli |
| Skin biopsy | Confirms the type histologically |
| Nerve biopsy | In pure neuritic leprosy |
| Lepromin (Mitsuda) test | Assesses cell-mediated immunity; positive in tuberculoid and negative in lepromatous leprosy; prognostic, not diagnostic |
| PCR | Detects M. leprae DNA in research and difficult cases |
Test
Clinical examination
Purpose
Skin patches, sensory testing, palpation of peripheral nerves
Test
Slit-skin smear
Purpose
Detects acid-fast bacilli; the bacteriological index (BI) measures bacterial load on a 0 to 6+ scale, and the morphological index (MI) estimates the proportion of live, solidly staining bacilli
Test
Skin biopsy
Purpose
Confirms the type histologically
Test
Nerve biopsy
Purpose
In pure neuritic leprosy
Test
Lepromin (Mitsuda) test
Purpose
Assesses cell-mediated immunity; positive in tuberculoid and negative in lepromatous leprosy; prognostic, not diagnostic
Test
PCR
Purpose
Detects M. leprae DNA in research and difficult cases
Management
Multidrug Therapy (MDT) in India
India revised its classification and treatment protocol in line with WHO recommendations and implemented it nationwide from 1 April 2025. A three-drug regimen of rifampicin, dapsone and clofazimine is now used for both PB and MB leprosy.
| Group | Drugs | Duration (WHO) |
|---|---|---|
| Paucibacillary | Rifampicin, dapsone, clofazimine | 6 months |
| Multibacillary | Rifampicin, dapsone, clofazimine | 12 months |
Group
Paucibacillary
Drugs
Rifampicin, dapsone, clofazimine
Duration (WHO)
6 months
Group
Multibacillary
Drugs
Rifampicin, dapsone, clofazimine
Duration (WHO)
12 months
Doses and blister packs differ for adults and children. Follow the current National Leprosy Eradication Programme (NLEP) guidelines.
Antileprosy Drugs
| Drug | Mechanism | Key Adverse Effects |
|---|---|---|
| Rifampicin | Inhibits bacterial DNA-dependent RNA polymerase; strongly bactericidal | Orange-red body fluids, hepatotoxicity, drug interactions |
| Dapsone | Inhibits folate synthesis | Haemolysis (especially in G6PD deficiency), methaemoglobinaemia, dapsone hypersensitivity syndrome |
| Clofazimine | Binds mycobacterial DNA; also anti-inflammatory | Reddish-brown skin pigmentation, dry skin, gastrointestinal upset |
Drug
Rifampicin
Mechanism
Inhibits bacterial DNA-dependent RNA polymerase; strongly bactericidal
Key Adverse Effects
Orange-red body fluids, hepatotoxicity, drug interactions
Drug
Dapsone
Mechanism
Inhibits folate synthesis
Key Adverse Effects
Haemolysis (especially in G6PD deficiency), methaemoglobinaemia, dapsone hypersensitivity syndrome
Drug
Clofazimine
Mechanism
Binds mycobacterial DNA; also anti-inflammatory
Key Adverse Effects
Reddish-brown skin pigmentation, dry skin, gastrointestinal upset
Before Starting MDT
- Treat jaundice and anaemia first or alongside
- Avoid dapsone in patients allergic to sulpha drugs and refer for an alternative regimen
- Adjust for patients already taking rifampicin for tuberculosis
Disability Prevention and Rehabilitation
- Self-care for anaesthetic hands and feet (soaking, oiling, inspection, protective footwear)
- Eye care for lagophthalmos
- Physiotherapy and reconstructive surgery for deformities
- Social support to reduce stigma
Prevention and Control (Community Medicine Angle)
| Measure | Key Points |
|---|---|
| Early case detection | Active case finding and awareness campaigns |
| Complete MDT | Cures patients and stops transmission |
| Contact screening | Examination of household and neighbourhood contacts |
| Post-exposure prophylaxis | Single-dose rifampicin for eligible contacts under the programme |
| Disability prevention | Early treatment of reactions and neuritis |
| Reducing stigma | Health education and social inclusion |
Measure
Early case detection
Key Points
Active case finding and awareness campaigns
Measure
Complete MDT
Key Points
Cures patients and stops transmission
Measure
Contact screening
Key Points
Examination of household and neighbourhood contacts
Measure
Post-exposure prophylaxis
Key Points
Single-dose rifampicin for eligible contacts under the programme
Measure
Disability prevention
Key Points
Early treatment of reactions and neuritis
Measure
Reducing stigma
Key Points
Health education and social inclusion
National programme: The National Leprosy Eradication Programme (NLEP) aims to stop leprosy transmission at the sub-national level by 2027. It has also set up a national antimicrobial resistance surveillance network for MDT drugs.
Prognosis
Leprosy is curable with MDT, and patients stop being infectious soon after starting treatment. Nerve damage that has already occurred may be permanent, so early diagnosis and prompt treatment of reactions are the keys to preventing disability.
Quick Viva Questions
Q: Which nerve is most commonly thickened in leprosy? A: The ulnar nerve.
Q: In which animals can M. leprae be grown? A: The mouse footpad and the nine-banded armadillo.
Q: What is a Grenz zone? A: A clear band of dermis just below the epidermis, seen in lepromatous leprosy.
Q: What is the lepromin test used for? A: It assesses cell-mediated immunity and has prognostic value; it is not diagnostic.
Q: Which drug in MDT causes skin pigmentation? A: Clofazimine.
Q: What is the treatment of a type 1 lepra reaction? A: Corticosteroids, alongside continued MDT.
How Leprosy Appears in MBBS University Exams
Typical question styles (not attributed to specific papers or years):
- "Classify leprosy. Describe the clinical features, diagnosis and treatment of lepromatous leprosy." (Long essay, Medicine)
- "Describe the laboratory diagnosis of leprosy." (Short note, Microbiology)
- "Differentiate tuberculoid from lepromatous leprosy." (Short answer, Pathology)
- "Write a short note on lepra reactions." (Short note)
- "Write a short note on multidrug therapy for leprosy." (Short note, Pharmacology)
- "Describe the National Leprosy Eradication Programme." (Long essay, Community Medicine)
Frequently Asked Questions
What are the cardinal signs of leprosy?
A hypopigmented or reddish skin patch with definite loss of sensation, a thickened peripheral nerve with sensory or motor loss, and acid-fast bacilli in a slit-skin smear. Any one confirms a case.
What is the current treatment of leprosy in India?
Since 1 April 2025, India uses three-drug MDT (rifampicin, dapsone and clofazimine) for both paucibacillary and multibacillary leprosy, as per NLEP guidelines. WHO recommends 6 months for PB and 12 months for MB.
Can I download the leprosy PPT for my presentation?
Yes. Use the Download PPT button at the top of this page. The GeckoMed app also gives offline access to the slides and notes.
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