Leprosy

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A traditional much feared disfiguring chronic bacterial infection of the skin and peripheral nerves caused by Mycobacterium leprae.

Contents

Historical

Commonly referred to as Hansen's disease.

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Notifiable disease in England and Wales, but not Scotland or Ireland

Epidemiology

Younger adult males most at risk. Known in India by 600 BC. Introduced to Europe by 1400's. Most of the 200,000 odd registered cases worldwide are in Southeast Asia. Since effective treatment in 1982, it has a WHO strategic plan for the leprosy elimination which is proceeding at 4% per annum. As of 2009 most activity is in Angola, Brazil, Central African Republic, Democratic Republic of Congo, India, Madagascar, Mozambique, Nepal and Tanzania.

Aetiology

Mycobacterium leprae. There is evidence that the NOD2-mediated signalling pathway which regulates immune response can be an important host factor in determining susceptibility and also response. It shares this with Crohn's disease[1].

Clinical

Spectrum of disease from asymptomatic (most common) to tuberculoid and lepromatous. Rarely associated with [[glomerulonephritis, vasculitis, nerve palsy and granulomata anywhere (usually cooler areas body). For example, eyes can have lagophthalmos, corneal hypoaesthesia and iridocyclitis. Common qualifying terms are multibacillary (type 2 helper T (Th2) cell response active), paucibacillary (type 1 helper T (Th1) cells active) and borderline.

tuberculoid<--- borderline-tuberculoid---borderline-borderline---borderline-lepromatous--->lepromatous

IL-2,gamma interferon<----------------------------------cytokine profile------------------------------------>IL-4, IL-5, IL-10

Symptoms

Signs

The characteristic skin lesions in association with thickened nerves are diagnostic.

Tuberculoid

Large well defined macular hypopigmented/erythematous anaesthetic lesions with usually raised margins or occasionally scaly patches

Lepromatous

Widespread erythematous macules, papules or nodules.

Investigations

Slit-skin smear

  • WHO recommended

Biopsy

  • Small non‐necrotic granulomas
  • Acid and alcohol fast bacilli

Radiology

Tuberculin skin tests

A tuberculin skin test (TST) is performed by introducing tuberculin, a protein derived from mycobacteria, into the skin. Somebody with prior immunity to mycobacteria will produce a response to the test. A vigorous response may indicate current infection with a mycobacterium, most likely (in the UK) MTB.

Prevention

  • Early detection of the disease then treatment as human human spread only
  • BCG vaccine. The disease can be prevented by vaccination with BCG vaccine (which prevents leprosy more effectively than it does tuberculosis).

Treatment

  • WHO multidrug treatment. For adults:
  • Corticosteroids of leprous reactions and "silent neuropathies"
  • Comprehensive care for prevention of disabilities and rehabilitation


References

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