Write a short note on leprosy — classification, clinical features, reactions and treatment.
Definition
Leprosy (Hansen's disease) is a chronic granulomatous infection caused by Mycobacterium leprae, an obligate intracellular acid-fast bacillus with a generation time of 12–14 days and an incubation period of 2–5 years (up to 20 for tuberculoid forms). It affects principally the skin and peripheral nerves, and is the commonest treatable cause of peripheral neuropathy worldwide. India accounts for a large share of global new case detection, making it a high-yield examination topic.
Transmission is by droplet spread from untreated multibacillary patients via the upper respiratory tract; the bacillus cannot be cultured in vitro and grows preferentially in cooler body areas — ear lobes, nose, testes, superficial nerves — which determines the clinical distribution.
Classification
Ridley–Jopling (immunological spectrum) — determined by cell-mediated immunity:
| Type | CMI / Lepromin | Bacillary Load | Skin Lesions | Nerve Involvement |
|---|---|---|---|---|
| Tuberculoid (TT) | Strong / positive | Paucibacillary | Few (1–3), large, well-defined, anaesthetic, dry, hairless | Early, asymmetrical, thickened |
| Borderline (BT, BB, BL) | Intermediate, unstable | Variable | Intermediate numbers | Variable, prone to reactions |
| Lepromatous (LL) | Poor / negative | Multibacillary | Numerous, symmetrical, ill-defined, shiny; leonine facies, madarosis | Late, symmetrical, glove-and-stocking |
WHO operational classification (for treatment):
- Paucibacillary: 1–5 skin lesions, no bacilli on slit-skin smear.
- Multibacillary: more than 5 lesions, or any positive smear.
Clinical Features
The cardinal signs — any one establishes the diagnosis:
1. Hypopigmented or reddish skin patch with definite loss of sensation.
2. Thickened or tender peripheral nerve with loss of sensation or weakness in its distribution.
3. Acid-fast bacilli on slit-skin smear.
Nerves commonly involved: ulnar (at the elbow — the commonest), median, radial, common peroneal, posterior tibial, facial, and great auricular. Examine all systematically for thickening and tenderness.
Deformities result from nerve damage, not from the organism directly: claw hand (ulnar and median), wrist drop (radial), foot drop (common peroneal), lagophthalmos (facial nerve), trophic ulcers on anaesthetic soles, and resorption of digits.
Lepromatous features: diffuse infiltration, madarosis (loss of eyebrows, laterally first), nasal stuffiness and septal perforation with saddle-nose deformity, leonine facies, gynaecomastia, testicular atrophy, and ocular involvement causing iritis and blindness.
Lepra Reactions
Acute immunological episodes that are the main cause of nerve damage and disability, and a medical emergency.
| Feature | Type 1 (Reversal) | Type 2 (Erythema Nodosum Leprosum) |
|---|---|---|
| Mechanism | Type IV delayed hypersensitivity — increased CMI | Type III immune complex deposition |
| Occurs in | Borderline types (BT, BB, BL) | Lepromatous and BL disease |
| Skin | Existing lesions become erythematous, swollen and tender | Crops of new tender subcutaneous erythematous nodules on normal skin |
| Nerve | Acute neuritis — pain, tenderness, sudden loss of function | Neuritis less prominent |
| Systemic | Minimal | Fever, malaise, arthritis, iritis, orchitis, lymphadenopathy, nephritis |
| Treatment | Corticosteroids (prednisolone, tapered over months) | Corticosteroids; thalidomide highly effective (teratogenic — strict contraception); clofazimine |
Diagnosis
- Slit-skin smear from ear lobe and lesion edge, stained by modified Ziehl–Neelsen (Fite) stain, reported as the bacteriological index and morphological index.
- Skin biopsy for histopathology and nerve involvement.
- Nerve conduction studies and high-resolution ultrasound for subclinical neuropathy. The lepromin test is not diagnostic — it assesses immune status and classifies the spectrum.
Treatment — WHO Multidrug Therapy
MDT is provided free through the National Leprosy Eradication Programme (NLEP) in India. The regimens combine rifampicin, clofazimine and dapsone, given for 6 months in paucibacillary and 12 months in multibacillary disease, with monthly supervised and daily self-administered components. WHO now recommends a uniform three-drug regimen for all types.
Additional management: treat reactions promptly to prevent disability; physiotherapy, protective footwear and self-care education for anaesthetic limbs; reconstructive surgery for established deformity; contact screening and single-dose rifampicin post-exposure prophylaxis for contacts; and counselling to address the profound social stigma, which remains a major barrier to early presentation.
Nerve function loss in a lepra reaction is a medical emergency. Corticosteroids must be started immediately — delay of even a few weeks converts reversible neuritis into permanent deformity. A patient completing MDT is cured of infection but may still develop reactions afterwards, so follow-up must continue.
WHO MDT drug doses, duration and the current status of the uniform regimen and post-exposure prophylaxis — confirm against current NLEP and WHO guidance before publication.
All questions in Dermatology
- SN1Write a short note on cutaneous adverse drug reactions — patterns, causative drugs and management.
- SN2Write a short note on scabies.
- SN3Write a short note on psoriasis — types, clinical features, associations and management.
- SN4Write a short note on leprosy — classification, clinical features, reactions and treatment.
- SN5Write a short note on acne vulgaris.
- SN6Write a short note on urticaria and impetigo.
- SN7Write a short note on dermatophyte (tinea) infections.
- SN8Write a short note on pemphigus vulgaris and its differentiation from bullous pemphigoid.
- SN9Write a short note on erythema multiforme, Stevens-Johnson syndrome and toxic epidermal necrolysis.
- SN10Write a short note on atopic dermatitis (eczema).
- SN11Write a short note on the mucocutaneous manifestations of systemic lupus erythematosus.