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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+).

Leprosy Classification and Treatment

Clinical Manifestations - The Disease Unmasked

  • Skin & Nerve (Ridley-Jopling Spectrum):

    TypeSkin LesionsSensory LossNerve Involvement
    TT1-few, defined, anaesthetic macules/plaquesEarly, markedEarly, severe
    BTFew-mod, asymmetric, varied plaquesModerateProminent
    BBNum, polymorphic, annular/punchedModerateCommon, severe
    BLMany, ill-defined, shiny lesionsPatchy, less severeModerate, many
    LLDiffuse infiltration, nodules, madarosisLate, glove-stockingWidespread, 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). Leprosy histopathology: Virchow cells and globi
  • Lepromin Test: Assesses CMI; not diagnostic. Mitsuda (+ve in TT/BT): >5mm induration at 4 wks.
  • Management (WHO MDT):
    TypeRegimenDuration
    PBRIF (600mg monthly) + DAP (100mg daily)6 months
    MBRIF (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

FeatureType 1 (Reversal Reaction, RR)Type 2 (Erythema Nodosum Leprosum, ENL)
Mechanism↑ CMI (Type IV).Immune complex (Type III).
ClinicalInflamed lesions, neuritis.Tender nodules, fever, systemic.
OnsetDuring/after MDT.LL/BL; during/after MDT.
ManagementPrednisolone 40-60mg; NSAIDs.Clofazimine, Thalidomide 100-400mg; Steroids.
  • 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_

Practice Questions: Leprosy

Test your understanding with these related questions

Asymmetrical nerve thickening with several hypoesthetic macules on skin indicates which stage of leprosy:

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Flashcards: Leprosy

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Asymmetric nerve involvement is seen typically in _____ leprosy

TAP TO REVEAL ANSWER

Asymmetric nerve involvement is seen typically in _____ leprosy

tuberculoid

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