Leprosy (Hansen Disease)

Key Features

Essentials of Diagnosis

• Pale, anesthetic macular—or nodular and erythematous—skin lesions

• Superficial nerve thickening with resultant anesthesia

• History of residence in endemic area in childhood

• Acid-fast bacilli in skin lesions or nasal scrapings, or characteristic histologic nerve changes

General Considerations

• A chronic infectious disease caused by the acid-fast rod Mycobacterium leprae

• The mode of transmission probably is respiratory droplets and involves prolonged exposure in childhood

• The disease is divided into two distinct types: lepromatous and tuberculoid

• The lepromatous type occurs in persons with defective cellular immunity

• In the tuberculoid type, cellular immunity is intact and the course is more benign

Demographics

• The disease is endemic in tropical and subtropical Asia, Africa, Central and South America, and the Pacific regions

Clinical Findings

Symptoms and Signs

• The onset is insidious

• The lesions involve the cooler body tissues: skin, superficial nerves, nose, pharynx, larynx, eyes, and testicles

• Skin lesions may occur as

  • Pale, anesthetic macular lesions 1–10 cm in diameter

  • Discrete erythematous, infiltrated nodules 1–5 cm in diameter

  • Diffuse skin infiltration

• Neurologic disturbances are caused by nerve infiltration and thickening, with resultant anesthesia, and motor abnormalities

• Bilateral ulnar neuropathy is highly suggestive

LEPROMATOUS TYPE (MULTIBACILLARY LEPROSY)

• The course is progressive with nodular skin lesions and slow, symmetric nerve involvement

TUBERCULOID TYPE (PAUCIBACILLARY LEPROSY)

• The course is more benign and less progressive, with macular skin lesions and severe asymmetric nerve involvement of sudden onset

• Intermediate ("borderline") cases are frequent. Eye involvement (keratitis and iridocyclitis), nasal ulcers, epistaxis, anemia, and lymphadenopathy may occur

Differential Diagnosis

• Systemic lupus erythematosus

• Sarcoidosis

• Syphilis

• Erythema nodosum

• Erythema multiforme

• Cutaneous tuberculosis

• Vitiligo

Diagnosis

Laboratory Tests

• M leprae does not grow in artificial media but does grow in the footpads of armadillos

• The lepromatous type: abundant acid-fast bacilli in the skin lesions and a negative lepromin skin test

• The tuberculoid type: few bacilli present in the lesions and a positive lepromin skin test

Diagnostic Procedures

• Laboratory confirmation requires the demonstration of acid-fast bacilli in a skin biopsy

• Biopsy of skin or of a thickened involved nerve also gives a typical histologic picture

Treatment

Medications

• Combination therapy is recommended for treatment of all types of leprosy

• For borderline and lepromatous cases (ie, multibacillary disease), the World Health Organization recommends

  • A triple oral drug regimen of rifampin, 600 mg once a month; dapsone, 100 mg/day; and clofazimine, 300 mg ...