Mycobacterium leprae

Background

Microbiology

• Slow-growing acid-fast bacillus

Epidemiology

• About 1 million cases worldwide each year, but is rare in North America
  • Number may be underestimated due to difficulties with reliable diagnosis
• Most commonly occurs in Southeast Asia (especially India) and Brazil
• Decreasing incidence over the past several decades, likely due to short-course multidrug therapy starting in 1982
• Humans are thought to be the main reservoir, but it has been found in animals as well (particularly armadillos)
• Transmitted most likely by respiratory droplets, though can also be transmitted by direct contact, transplacentally, through breast milk, and after animal exposure

Risk Factors

• Age, with peaks in adolescence and ≥30 years
• Adult men (compared to adult women)
• Duration of contact with an infected patient, and the burden of bacilli in the patient

Clinical Presentation

• Incubation period of 3-5 years (with wide range)
• Classic presentation is anaesthetic hypopigmented skin lesion with thickened nerves
• Clinical spectrum from tuberculoid, paucibacillary disease to lepromatous, multibacillary disease
  • Paucibacillary (PB) disease has 1 to 5 skin lesions, without bacilli on skin slit smear
  • Multibacillary (MB) disease has more than 5 skin lesions, with or without nerve involvement or bacilli on slit-skin smear (regardless of number of lesions)

Management

Disease	Treatment
Paucibacillary	6 months of rifampin, dapsone, and clofazimine
Multibacillary	12 months of rifampin, dapsone, and clofazimine
Rifampin resistance	6 months of at least two second-line drugs with clofazimine, followed by 18 months of one second-line drug with clofazimine
Quinolone resistance	As for rifampin resistance, but without a fluoroquinolone

Second-line antibiotics

• Clarithromycin
• Minocycline
• Fluoroquinolones