Leprosy

Etiopathogenesis & Classification - Foe & Its Forms

• Etiopathogenesis:

  • Agent: Mycobacterium leprae (acid-fast bacillus).
  • Optimal Temp: 30-33°C (favours cooler body parts: skin, peripheral nerves).
  • Transmission: Primarily respiratory droplets from untreated MB cases; prolonged close contact.
  • Incubation Period: Long, average 2-5 years (can range from months to 20 years).

  ⭐ M. leprae is an obligate intracellular parasite and cannot be cultured on standard artificial media.

• Classification Systems:

  • Ridley-Jopling (R-J) Spectrum: Based on cellular immunity.
    • Tuberculoid (TT), Borderline Tuberculoid (BT), Mid-Borderline (BB), Borderline Lepromatous (BL), Lepromatous (LL).
    • 📌 Mnemonic: Tuberculoid Tough, Lepromatous Lousy, Borderlines Bad.
  • WHO Classification (for treatment): Based on number of skin lesions & Bacteriological Index (BI).
    • Paucibacillary (PB): ≤5 skin lesions AND skin smear negative (or BI < 2+).
    • Multibacillary (MB): >5 skin lesions OR nerve involvement (neuritis) OR skin smear positive (BI ≥ 2+).

Clinical Manifestations - The Disease Unmasked

• Skin & Nerve (Ridley-Jopling Spectrum):

  Type	Skin Lesions	Sensory Loss	Nerve Involvement
  TT	1-few, defined, anaesthetic macules/plaques	Early, marked	Early, severe
  BT	Few-mod, asymmetric, varied plaques	Moderate	Prominent
  BB	Num, polymorphic, annular/punched	Moderate	Common, severe
  BL	Many, ill-defined, shiny lesions	Patchy, less severe	Moderate, many
  LL	Diffuse infiltration, nodules, madarosis	Late, glove-stocking	Widespread, late

• Nerve Damage:

  • Affected Nerves: Ulnar, Median, Radial, Common Peroneal, Posterior Tibial, Facial, Great Auricular.
  • Signs: Thickened nerves, tenderness; motor loss (e.g., claw hand, foot drop); sensory loss; trophic ulcers; deformities (e.g., lagophthalmos).

• Other: Eye (corneal ulcers, blindness), Testicular atrophy (LL).

⭐ Leonine facies is a characteristic feature of lepromatous leprosy.

Diagnosis & Management - Spotting & Stopping

• Cardinal Signs:
  • Skin patches (hypopigmented/erythematous) + definite sensory loss.
  • Thickened peripheral nerve(s).
  • AFB in SSS/biopsy.
• Slit-Skin Smear (SSS):
  • Sites: Earlobes, lesions.
  • Bacteriological Index (BI): Bacillary load (0-6+).
  • Morphological Index (MI): Viable bacilli %.
• Skin Biopsy: Histopathology for classification (TT/BT: granulomas; LL/BL: Virchow cells, globi).
• Lepromin Test: Assesses CMI; not diagnostic. Mitsuda (+ve in TT/BT): >5mm induration at 4 wks.
• Management (WHO MDT):

  Type	Regimen	Duration
  PB	RIF (600mg monthly) + DAP (100mg daily)	6 months
  MB	RIF (600mg monthly) + CLO (300mg monthly, 50mg daily) + DAP (100mg daily) (📌 RDC)	12 months

⭐ SLPB: Single dose Rifampicin (600mg) + Ofloxacin (400mg) + Minocycline (100mg) (ROM).

Lepra Reactions & Prevention - Fiery Flare-ups & Control

• NLEP Key Strategies:
  • Early case detection & prompt MDT.
  • High MDT coverage.
  • Disability Prevention & Medical Rehabilitation (DPMR).
  • IEC activities.
  • ASHA's role: awareness, case finding, referral.

⭐ Thalidomide: DOC for severe or recurrent ENL. ⚠️ Teratogenic; contraindicated in pregnancy.

High‑Yield Points - ⚡ Biggest Takeaways

• Caused by M. leprae (acid-fast); affects skin & peripheral nerves.
• Key signs: anesthetic skin lesions, thickened nerves, positive slit-skin smear (SSS).
• Spectrum: Tuberculoid (TT) (PB, strong CMI) to Lepromatous (LL) (MB, weak CMI).
• Lepra reactions: Type 1 (Reversal) & Type 2 (ENL) are acute immune events.
• Multidrug Therapy (MDT) is crucial for both Paucibacillary (PB) & Multibacillary (MB).
• Nerve damage leads to characteristic deformities and disability.
• SSS for Bacteriological Index (BI) aids diagnosis and monitors treatment_response_