What are the skin manifestations, associated nerve involvement, and pathological findings of leprosy, and what investigations are used to diagnose a case of leprosy (Hansen's disease)?

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Last updated: March 17, 2025View editorial policy

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From the Research

Leprosy, caused by Mycobacterium leprae, presents with various skin manifestations, including hypopigmented or erythematous patches with reduced sensation in tuberculoid leprosy, and more widespread, symmetrical, and numerous lesions in lepromatous leprosy, with nerve involvement affecting peripheral nerves and leading to sensory loss, muscle weakness, and deformities. The skin manifestations of leprosy can vary depending on the type, with borderline forms showing intermediate features.

  • The most common skin manifestations include:
    • Hypopigmented or erythematous patches with reduced sensation in tuberculoid leprosy
    • More widespread, symmetrical, and numerous lesions in lepromatous leprosy
  • Nerve involvement is a hallmark of leprosy, affecting peripheral nerves like the ulnar, median, radial, common peroneal, and facial nerves, leading to sensory loss, muscle weakness, and deformities. Pathologically,
  • tuberculoid leprosy shows granulomatous inflammation with few bacilli,
  • while lepromatous leprosy demonstrates numerous bacilli within foamy macrophages (Virchow cells) 1. For diagnosis,
  • slit-skin smears from lesions or earlobes are essential to detect acid-fast bacilli using Ziehl-Neelsen stain, with bacterial index assessment,
  • skin biopsy confirms diagnosis and classifies the type,
  • PCR can detect M. leprae DNA in tissues,
  • nerve conduction studies help assess nerve damage,
  • and Lepromin test indicates host immune response but isn't diagnostic 2, 3. Treatment involves multidrug therapy, with the most recent and effective regimen being monthly rifampin, moxifloxacin, and minocycline (RMM) for 12-24 months, as it has shown rapid improvement of skin lesions and no significant side effects 2. Early diagnosis and treatment are crucial to prevent disabilities, with regular follow-up to monitor for reactions and relapse.
  • The clinical profile of leprosy patients can vary, with the highest incidence noted in the 17-40 years age group, and a male to female ratio of 1.7:1 3.
  • Alternative therapies, such as clarithromycin, can be considered for patients who are resistant or allergic to rifampicin, as it has shown efficacy in multibacillary leprosy therapy 4.

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