40. LEPROSY

Introduction

Leprosy, also known as Hansen’s disease, is a chronic infectious disease caused by Mycobacterium leprae or M. lepromatosis. It develops very slowly (from 6 months to even 40 years) and mainly affects the skin, peripheral nerves and cooler parts of the body such as eyes, nose, earlobes, hands, feet and testes. If untreated, it leads to deformities and disability.

Leprosy is a chronic granulomatous disease similar to tuberculosis because it produces long-term inflammatory nodules (granulomas). Human-to-human transmission is most common, usually through nasal droplets. Rarely, animals like armadillos, chimpanzees and mangabey monkeys may transmit infection.

Classification

Leprosy is broadly classified into three clinical groups:

1. Paucibacillary (PB) / Tuberculoid Leprosy

  • Few (1–5) hypopigmented or hyperpigmented skin patches.
  • Loss of sensation in skin lesions due to nerve involvement.
  • Peripheral nerve thickening may be felt in areas like ulnar nerve, peroneal nerve, posterior tibial, median, radial nerve, etc.
  • Stronger immune response → fewer bacteria.

2. Multibacillary (MB) / Lepromatous Leprosy

  • Multiple, symmetrical skin lesions that may not show loss of sensation.
  • Presence of nodules, plaques and diffuse skin thickening.
  • Nasal mucosa involvement → nose blockage and bleeding.
  • Ulcerated nodules show large numbers of acid-fast bacilli inside macrophages.
  • Weak immune response → high bacterial load.

3. Borderline / Dimorphous Leprosy

  • Most common type.
  • Features overlap between PB and MB types.
  • More widespread lesions and nerve involvement than PB.

Pathogenesis

Leprosy begins slowly and primarily affects nerves, skin and eyes. Other organs like mucosa, testes, kidney, muscles and blood vessels may also be affected.

  • Bacteria enter the body through the respiratory tract.
  • Most infected people never develop disease because M. leprae has low pathogenicity.
  • Bacilli migrate to peripheral nerves and enter Schwann cells.
  • They multiply slowly (divide every 12–14 days).
  • Bacteria spread to new cells after destroying old ones.
  • Immune system recognizes infection once bacterial load increases.
  • Outcome depends on cell-mediated immunity (CMI):
    • Strong immunity → PB leprosy (localized, fewer lesions)
    • Poor immunity → MB leprosy (widespread, high bacterial load)
  • Leprosy reactions (Type 1 & Type 2) occur due to sudden immune changes during treatment or immune recovery.

Epidemiology

  • Common in India, Brazil, Indonesia, Congo, Madagascar, Mozambique and Nepal.
  • About 2.5 lakh new cases were reported globally in 2008.
  • Transmission mainly occurs through inhalation of infected nasal droplets.
  • Large numbers of bacilli are seen in nasal secretions of MB patients.

Signs and Symptoms

Skin Symptoms

  • Flat, pale or discoloured patches with numbness.
  • Skin nodules or growths.
  • Thick, stiff or dry skin.
  • Painless ulcers on feet.
  • Swollen or lumpy areas on face/earlobes.
  • Loss of eyebrows or eyelashes.

Nerve Symptoms

  • Numbness or loss of sensation.
  • Muscle weakness or paralysis (hands/feet).
  • Enlarged peripheral nerves (at elbow, knee or neck).
  • Eye problems leading to blindness.

Mucosal Symptoms

  • Nasal congestion
  • Nosebleeds

Advanced Untreated Cases

  • Hand/foot deformities
  • Shortening of fingers/toes due to reabsorption
  • Chronic, non-healing ulcers
  • Blindness
  • Nose disfigurement
  • Painful nerves and burning sensation

Diagnosis

  • Clinical diagnosis based on:
    • Skin patches with loss of sensation
    • Thickened peripheral nerves
    • Both features together
  • Skin smear or biopsy showing acid-fast bacilli (Ziehl-Neelsen or Fite stain).
  • Paucibacillary cases: few/no bacilli in smear.
  • Multibacillary cases: abundant bacilli in smear.
  • Special tests (done in advanced labs): lepromin test, PGL-1 antibody test, PCR.
  • Additional tests: CBC, LFT, creatinine, nerve biopsy if needed.

Treatment

The WHO recommends MDT (multi-drug therapy). Early treatment stops transmission and prevents disability.

Paucibacillary Leprosy (PB)

  • Dapsone + Rifampicin
  • Duration: at least 6 months

Multibacillary Leprosy (MB)

  • Dapsone + Rifampicin + Clofazimine
  • Duration: 12 months or more

Additional Notes

  • Steroids are used for painful nerve inflammation or leprosy reactions.
  • Early treatment stops progression, but existing deformities may not reverse.
  • WHO allows single-dose therapy (rifampicin + ofloxacin + minocycline) for single-lesion leprosy.

Complications

  • Blindness or glaucoma
  • Facial disfigurement
  • Infertility in men
  • Kidney damage
  • Claw hand or foot drop
  • Nasal collapse and chronic nose blockage
  • Irreversible peripheral nerve damage

Prevention

  • Early detection and treatment to stop spread.
  • Public education to reduce stigma and encourage early consultation.
  • Close monitoring of household contacts.
  • Single-dose rifampicin prophylaxis for close contacts (57% effective for first 2 years).
  • No fully protective vaccine available; BCG offers partial protection.

Detailed Notes:

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