Overview
- Leprosy is a slowly progressive, chronic, systemic infectious disease that primarily affects the skin and peripheral nerves.
- Causative Organism: Mycobacterium leprae
- Source: Infected cases (humans, armadillos, sphagnum moss)
Sources
- Infected humans
- Armadillos
- Sphagnum moss
Mode of Transmission
- Respiratory droplet inhalation
- Contact with broken skin
- Amoeba insect vectors
- Transplacental transmission
- Breastfeeding
- Tattoos, cornea, organ transplantation
Incubation Period
- Range: 2-40 years
- Average: 5-7 years
Pathogenesis
| Leprosy |
|---|
| Entrance of Mycobacterium leprae |
| ↓ |
| Mycobacteria engulfed by macrophages |
| ↓ |
| Dissemination into blood |
| ↓ |
| Mycobacterial replication in cool tissues such as skin and peripheral nerves |
| ↓ |
| TH response |
| ↓ |
| Chronic granulomatous inflammation |
Epidemiology
| Indicator | Statistics |
|---|---|
| Annual New Case Detection Rate (ANCDR) | 9.27/Lac |
| Prevalence | 0.67/10,000 |
| Elimination Level | <1 case/10,000 (December 2005) |
Clinical Presentation
Skin Involvement:
- Various skin lesions and thickening.
Peripheral Nerves:
| Feature | Details |
|---|---|
| Peripheral Neuropathy | Peripheral nerve degeneration → Peripheral nerve enlargement |
| Most Common Nerve Involved | Ulnar nerve |
| Most Common Cranial Nerve Involved | Facial nerve |
| Most Common Deformity | Claw hand |
| Best Nerve for Biopsy | Superficial radial cutaneous nerve > Sural nerve |
| Earliest Sensation Lost | Cold & heat differentiation → Cold → Heat → Fine touch → Pain → Crude touch |
| Sensation Never Lost | Proprioception or vibration |
Viscera Involvement:
- Most commonly involved organ (Males): Testis (Males), Liver (Females)
- Least commonly involved organ (Males): CNS (Males), Uterus (Females)
Clinical Patterns Based on TH Cell Response
| Feature | Tuberculoid Leprosy | Lepromatous Leprosy |
|---|---|---|
| Severity | Less severe | More severe |
| Immunity | Good (CMI) | Poor → Most infectious |
| Immune Response | Strong TH1 response | Weak TH1 response, More TH2 response |
| Skin | Sharply demarcated hypopigmented macules or plaques | Hypoesthetic or anesthetic macular, papular, or nodular skin lesions |
| Peripheral Nerves | Asymmetric involvement of large peripheral nerves | Symmetrical involvement of peripheral nerves |
| Systemic Involvement | Rare | Common (e.g., Testes, Upper airways) |
| Lepromin Skin Test | Positive | Negative |
| Ridley-Jopling Classification | True tuberculoid (TT), Borderline tuberculoid (BT) | Lepromatous leprosy (LL), Borderline lepromatous (BL) |
Leprosy Classification: Paucibacillary vs. Multibacillary
| Feature | Paucibacillary | Multibacillary |
|---|---|---|
| Skin Lesions | ≤5 | >5 |
| Nerve Involved | 0-1 | ≥1 |
| SSS: AFB | Absent | Present |
Clinical Spectrum
- Most common type in India: Borderline tuberculoid (BT)
- Most common type in children: Intermediate type
Special Types of Leprosy
| Special Type | Clinical Features | Histopathology |
|---|---|---|
| Leonine Leprosy | Diffuse nodular lepromatous leprosy with “lion-like” facial appearance (Leonine facies). | Diffuse infiltration of foamy macrophages, granulomatous inflammation. |
| Lepra Bonita (Lucio Leprosy) | Diffuse skin infiltration, loss of hairs, eyebrows, and eyelashes; shiny skin; patient appears younger. | No granuloma; foamy macrophages filled with acid-fast bacilli (AFB). |
| Histoid Leprosy | Dome-shaped papules on normal skin; often associated with dapsone resistance; no infiltration. | Spindle-shaped foamy cells, dense dermal histiocytic infiltrate. |
| Lozarine Leprosy | Characterized by diffuse skin ulcers, typically in undernourished individuals. | Vascular and neural involvement with extensive skin ulceration. |
| Indeterminate Hansen | Hypopigmented, non-scaly patches; normal sensation and sweating; no nerve thickening. | No specific histological pattern; potential to progress to a definitive form. |
| Pure Neuronal Hansen | Absence of skin lesions; primarily involves peripheral nerves; symptoms include tingling and numbness. | Nerve thickening with possible demyelination on nerve conduction studies. |
Lepra Reactions
| Type | Features | Treatment |
|---|---|---|
| Type 1 Lepra Reactions (Downgrading & Reversal) | – Type IV hypersensitivity – Seen in borderline leprosy (BT, BB, BL) – Dermal edema, FB giant cells, Plasma cells | Corticosteroids (DOC), NSAIDs, Chloroquine, Clofazimine |
| Type 2 Lepra Reactions (Erythema Nodosum Leprosum, ENL) | – Type III hypersensitivity – Seen in LL >> BL – New, recurrent crops of painful erythematous papules & nodules all over body | Corticosteroids (DOC), NSAIDs, Thalidomide, Clofazimine |
| Type 3 Lepra Reactions (Lucio’s Phenomenon) | – Seen in Lucio leprosy – Acute necrotizing vasculitis | High dose steroids |
Diagnosis
| Method | Details |
|---|---|
| Biopsy → HPE | Histopathological Examination (IOC) |
| Split-skin smear (SSS) | 10000 bacilli per gm of tissue Best site: — Untreated case: Ear lobe, — Treated case: Dorsum of fingers |
| Lepromin Test | Antigen: Heat-killed M. leprae (Lepromin), Dharmendra antigen |
Treatment
| Leprosy Type | Treatment Regimen | Duration | Follow-up |
|---|---|---|---|
| Paucibacillary | Rifampicin: 600 mg Once a Month Supervised (OAMS) Dapsone: 100 mg daily, unsupervised Clofazimine: 300 mg OAMS + 50 mg daily, unsupervised | 6 Months | 2 Years |
| Multibacillary | Rifampicin: 600 mg Once a Month Supervised (OAMS) Dapsone: 100 mg daily, unsupervised Clofazimine: 300 mg OAMS + 50 mg daily, unsupervised | 12 Months | 5 Years |
MDT completed but no change in lesions: Stop MDT and reassure patient. Bacteriological recovery may not coincide with clinical recovery.
National Leprosy Eradication Programme (NLEP)
| Feature | Details |
|---|---|
| SET Centre | Survey, Education & Treatment Centre |
| SIS | Simplified Information Systems |
| NIKUSTH | Online software for monitoring leprosy patients |
| Sapna | Mascot developed to spread awareness in community through key IEC messages |
| SLAC | Sparsh Leprosy Awareness Campaigns |
