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MI5.{2,5} | Bone & Joint Infections and Leprosy — SDL Guide (Part 3)

Leprosy — Treatment (MDT) & Prevention

A three-panel medical diagram explains PB and MB leprosy classification, WHO multi-drug therapy regimens, and prevention measures including early detection, contact screening, BCG, and disability prevention. — **Panel A:** PB leprosy: 1-5 lesions, BI negative; MB leprosy: more than 5 lesions, BI positive; anesthetic skin patches; slit-skin smear icon.. **Panel B:** PB MDT regimen with rifampicin and dapsone for 6 months; MB MDT regimen with rifampicin, clofazimine, and dapsone for 12 months; free MDT in India.. **Panel C:** Early detection of anesthetic patch, peripheral nerve thickening check, treatment adherence calendar, household contact screening, BCG partial protection, hand and foot disability prevention..

Multi-Drug Therapy (MDT) — WHO regimen, provided free of charge in India:

Classification	Regimen	Duration
Paucibacillary (PB): 1–5 lesions, BI negative	Rifampicin 600 mg once/month + Dapsone 100 mg/day	6 months
Multibacillary (MB): >5 lesions, BI positive	Rifampicin 600 mg once/month + Clofazimine 300 mg once/month + Dapsone 100 mg/day + Clofazimine 50 mg/day	12 months

Mechanism of key drugs:
- Rifampicin: RNA polymerase inhibitor; bactericidal; given as supervised monthly pulse
- Dapsone: Inhibits dihydropteroate synthase (DHPS); bacteriostatic; resistance emerging
- Clofazimine: Binds to DNA, anti-inflammatory; also active against M. avium; causes skin discolouration (red-brown)

Prevention:
- BCG vaccination provides partial protection against leprosy (60–80% efficacy in India — higher than its tuberculosis efficacy in India)
- Single-dose rifampicin (SDR) post-exposure prophylaxis for close contacts of new PB cases — WHO endorsed
- National Leprosy Eradication Programme (NLEP) — active case detection, MDT distribution

Other Mycobacterial skin infections:
- M. ulcerans — Buruli ulcer (West Africa, Queensland); necrotising skin ulcer; mycolactone toxin; treat with rifampicin + streptomycin
- M. marinum — fish tank granuloma; swimming pool exposure; nodular lesions on dorsum of hand; treat with minocycline or clarithromycin
- M. chelonae / M. abscessus — rapid-growing NTM; injection site abscess; liposuction complications; post-procedure outbreaks

CLINICAL PEARL

The Grenz zone is specific to leprosy: In lepromatous leprosy histopathology, a clear band of normal-appearing collagen separates the epidermis from the granulomatous infiltrate below — this is the Grenz zone ('border zone' in German). No other granulomatous skin disease has this feature. Combine Grenz zone + foam cells + AFB = leprosy. This is a pathology slide MCQ favourite across all post-MBBS entrance examinations.

Interactive practice: Multiple Choice

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