What is leprosy

Overview

Leprosy, also known as Hansen's disease, is a chronic infectious disease caused by the bacterium Mycobacterium leprae. The disease primarily affects the skin and peripheral nerves, causing progressive damage that can lead to severe disfigurement and disability if untreated. Despite its stigmatized history, leprosy is curable with modern antibiotics and preventable with early detection and treatment.

Historical Context

Leprosy has affected humanity for thousands of years, documented in ancient Egyptian, Indian, Chinese, and Biblical texts. During medieval Europe, leprosy was greatly feared and patients were isolated in leprosariums (leper colonies). The disease contributed significantly to stigma and social exclusion throughout history. However, the discovery of effective treatments in the 20th century and improved understanding of transmission have dramatically changed management and public health approaches.

Transmission and Epidemiology

Leprosy spreads through respiratory droplets from untreated patients with the lepromatous form. Approximately 95% of people are naturally immune and will not develop disease despite exposure. Infection requires prolonged, close contact with untreated patients over months. Currently, about 160,000 new cases occur annually worldwide, primarily in tropical and subtropical regions. India, Indonesia, and Brazil account for the majority of cases. The disease affects males more than females, typically in adults rather than children.

Types and Clinical Manifestations

Leprosy occurs in different forms based on immune response:

• Tuberculoid leukemia: Strong immune response; few skin lesions, limited nerve damage; minimal bacilli
• Borderline tuberculoid: Moderately strong immune response; some skin lesions and mild nerve damage
• Mid-borderline: Intermediate immune response; moderate skin lesions and nerve involvement
• Borderline lepromatous: Weak immune response; many skin lesions, significant nerve damage
• Lepromatous leprosy: Very weak immune response; extensive skin involvement, severe nerve damage, numerous bacilli

Diagnosis and Treatment

Diagnosis: Clinical examination of characteristic skin lesions and nerve involvement, skin biopsy or slit-skin smear showing acid-fast bacilli, lepromin test assessing immune response. Treatment: Multidrug therapy (MDT) combining rifampicin, dapsone, and clofazimine cures leprosy. Tuberculoid cases require 6 months of MDT; lepromatous cases require 12 months. Patients become non-infectious within 2 weeks of treatment initiation. Early treatment prevents permanent nerve damage and disability.

Prevention and Modern Status

Preventing leprosy involves early detection and treatment of cases, particularly in endemic areas. Close contacts of confirmed cases typically receive preventive antibiotics. No effective vaccine currently exists, though BCG vaccine provides some protection. The World Health Organization has nearly eliminated leprosy as a public health problem through multidrug therapy distribution. Many countries have zero or near-zero case burdens. However, continued vigilance remains necessary in endemic regions to achieve WHO's 2030 elimination target.