• See Also
  1. Mycobacteria
  2. Mycobacterium tuberculosis
  • Epidemiology
  1. Children more vulnerable to infection than adults
  2. Immunity in 95% of patients
  3. Incidence
    1. Worldwide 250,000/year
    2. U.S.: 225/year
      1. Most cases were acquired outside of the U.S. (e.g. Immigrants)
      2. Rare in the United States
        1. Most U.S. cases are in Florida, Texas, Louisiana, Hawaii, California
  4. Most commonly affected endemic regions
    1. Brazil
    2. India
    3. Indonesia
    4. Madagascar
    5. Myanmar (Burma)
    6. Nepal
  • Pathophysiology
  1. Mycobacterium leprae
    1. Acid fast bacilli
    2. Facultative Intracellular Bacteria
  2. Chronic Granulomatous infection
  3. Incubation: 3 to 20 years
  4. Growth best in cooler parts of body at 35.6C (96.0F), closer to the skin surface
  5. Severity of Leprosy is related to the strength of the host's cell mediated Immunity
    1. Greater cell mediated Immunity helps to contain the Bacteria
    2. However, greater cell mediated Immunity also results in Granuloma formation in the skin and nerve tissue
  6. Transmission
    1. Nasal or respiratory secretions from untreated patients
    2. Direct contact with infected skin lesions may also transmit infection
    3. Low risk from casual and household contact
    4. Most exposed patients do not develop Leprosy
  • Types
  1. Tuberculoid Leprosy (intact cellular Immunity)
    1. Localized, superficial, unilateral skin lesions (1-2) and nerve effects
    2. Nerve changes predominate
    3. Noninfectious
    4. Spontaneous recovery is most common
  2. Lepromatous Leprosy (defective cellular Immunity)
    1. Most severe form of Leprosy (due to decreased cell mediated response)
    2. High Bacterial loads (infectious)
    3. Skin changes predominate
      1. Extensive bilateral symmetric Macules and Papules
    4. Other involvement
      1. Also affects nerve, eye and testicular tissue
      2. Diffuse multisystem infection (including respiratory)
      3. Fatal in untreated patients
  3. Other Borderline Types
    1. Borderline Lepromatous
    2. Borderline
    3. Borderline Tuberculoid
  • Signs
  1. Skin lesions
    1. Types
      1. Macules or Papules, Nodules or Plaques
      2. Loss of hair within skin lesions
      3. Hypopigmented in dark skinned individuals
        1. May be hyperpigmented in other patients
      4. Sensation may be dulled in these areas
      5. Loss of lateral eyebrows
    2. Sites
      1. Face and ears
        1. Thickened facial skin is known as leonine facies (lion-like)
        2. Nasal cartilage destruction (saddlenose deformity)
      2. Wrists
      3. Buttocks
      4. Knees
    3. Spared areas (warm regions)
      1. Groin
      2. Axilla
      3. Hair covered scalp
  2. Nose and Throat changes
    1. Nasal symptoms to obstruction
    2. Laryngitis
    3. Hoarseness
  3. Neurologic changes
    1. Superficial Nerve tuberculoid changes (may be palpable)
      1. Ulnar Nerve
      2. Peroneal nerve
      3. Posterior tibial nerve
      4. Greater auricular nerve
    2. Effects
      1. Stocking Glove Peripheral Neuropathy
        1. Risk of repeated injury with secondary skin lesions and infections (similar to Diabetes Mellitus)
      2. Muscle atrophy
      3. Contractures
  4. Eye changes
    1. Corneal Ulcerations
    2. Blindness
  • Complications
  1. Crippling of hand (Worldwide most frequent cause)
  • Differential Diagnosis
  1. See Annular Lesions
  • Labs
  1. VDRL False Positive (10-20%)
  • Diagnosis
  1. Acid-fast stain (Fite method) for acid-fast bacilli
    1. Skin smears, or skin or nerve biopsy
    2. Bacteria abundant in Lepromatous Leprosy
  2. Skin lesion biopsy
    1. Tuberculoid Leprosy
      1. Epitheliod Granulomas
      2. Numerous peripheral Lymphocytes
    2. Lepromatous Leprosy
      1. Macrophages with foamy cytoplasm
  3. Polymerase Chain Reaction (PCR)
  4. Serology
    1. Lepromatous (95% Test Sensitivity)
    2. Tuberculoid (30% Test Sensitivity)
  5. Lepromin Skin Test
    1. Similar to PPD in Tuberculosis
    2. Measures the response to a superficial skin injection of Leprosy Protein extract
      1. Response suggests intact cell mediated Immunity and Tuberculoid Leprosy
  1. Background
    1. Guidelines listed are per U.S. NHDP (National Hansen's Disease Program)
    2. WHO guidelines use 3 drugs (Dapsone, Rifampin, Clofazimine) for all types, and for 6-12 months
    3. Fluoroquinolones are used in in place of Rifampin if resistant
    4. Reversal reactions (Type 1 Hypersensitivity Reaction to killed organisms)
      1. Occur in borderline patients (esp. in treatment year 1)
      2. Skin lesions become edematous and may ulcerate
      3. Motor or sensory neuritis may occur
      4. Treated with high dose Prednisone tapered over 2-6 months (or Methotrexate)
      5. Leprosy treatment must be continued despite reaction
    5. Erythema Nodosum (Type 2 Hypersensitivity Reaction to immune complex deposition)
      1. Occurs with any form of Leprosy
      2. May be accompanied by fever, Lymphadenopathy as well as neuritis, Arthritis, Orchitis, Iritis
      3. Treated with Prednisone on taper (or Methotrexate)
      4. Other agents (e.g. Thalidomide, Clofazimine) have also been used
      5. Leprosy treatment must be continued despite reaction
  2. Tuberculoid, Borderline Tuberculoid (Paucibacillary, BT)
    1. Dapsone 100 mg daily for 12 months AND
    2. Rifampin 600 mg daily for 12 months
  3. Lepromatous (or borderline/BB, borderline lepromatous/BL, may require indefinate treatment)
    1. Dapsone 100 mg daily for 24 months AND
    2. Rifampin 600 mg daily for 24 months AND
    3. Clofazimine 50 mg daily for 24 months
  • Prevention
  1. Post-exposure (age 15 years or older)
    1. Rifampin 600 mg orally for 1 dose
  • References
  1. Gladwin, Trattler and Mahan (2014) Clinical Microbiology, Medmaster, Fl, p. 189-91
  2. Miller in Wilson (1991) Harrison's IM, McGraw, p. 645-8
  3. (2025) Sanford Guide, accessed on IOS 3/11/2025
  4. Hsu (2001) Am Fam Physician 64(2):289-96 [PubMed]
  5. Wathen (1996) South Med J 89:647-52 [PubMed]