Leprosy (Hansen's Disease): Causes, Transmission, and Treatment

Leprosy is a chronic infectious disease caused by Mycobacterium leprae, an acid-fast bacillus. It primarily affects skin, peripheral nerves, upper respiratory mucosa, and eyes.

Transmission

• Prolonged close contact via respiratory droplets (not highly contagious).
• Incubation: months to 20+ years (average 5 years).
• 95% of people have natural immunity.

Clinical Forms (Ridley-Jopling Classification)

• Tuberculoid (paucibacillary): Few lesions, strong cell-mediated immunity, nerve damage prominent.
• Lepromatous (multibacillary): Many lesions, poor immunity, high bacterial load.
• Borderline forms: Intermediate, unstable.

Key Features

• Hypopigmented/erythematous skin patches with sensory loss.
• Thickened peripheral nerves (ulnar, peroneal, facial).
• Muscle weakness, claw hand, foot drop.
• Eye involvement (lagophthalmos, corneal anesthesia).
• Nasal collapse (lepra reaction).

Diagnosis

• Skin slit smear (acid-fast bacilli).
• Biopsy (granulomas, nerve involvement).
• PCR for M. leprae DNA.

Treatment: Multidrug Therapy (MDT) — WHO Regimen

• Paucibacillary: Dapsone + Rifampicin × 6 months.
• Multibacillary: Dapsone + Rifampicin + Clofazimine × 12 months.
• Free globally via WHO/Novartis.

Key Points

• Curable; early treatment prevents disability.
• Not hereditary; not spread by casual contact.
• Stigma remains a major barrier; education is crucial.
• Post-treatment reactions (Type 1 reversal, Type 2 ENL) need steroids/thalidomide.

Leprosy is a neglected tropical disease targeted for elimination (interruption of transmission).