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Leprosy

  • Author: Darvin Scott Smith, MD, MSc, DTM&H; Chief Editor: Michael Stuart Bronze, MD  more...
 
Updated: May 09, 2016
 

Background

Leprosy is a chronic infection caused by the acid-fast, rod-shaped bacillus Mycobacterium leprae. Leprosy can be considered 2 connected diseases that primarily affect superficial tissues, especially the skin and peripheral nerves. Initially, a mycobacterial infection causes a wide array of cellular immune responses. These immunologic events then elicit the second part of the disease, a peripheral neuropathy with potentially long-term consequences.

The social and psychological effects of leprosy, as well as its highly visible debilities and sequelae (as seen in the image below), have resulted in a historical stigma associated with leprosy. To minimize the prejudice against those with leprosy, the condition is also known as Hansen disease, named after G.A. Hansen, who is credited with the 1873 discovery of M leprae. This mycobacterium grows extremely slowly and has not been successfully cultured in vitro.

Hands with Z-thumbs, clawing, contractures, and sh Hands with Z-thumbs, clawing, contractures, and shortening of fingers due to repetitive injury and healing. Ho Chi Minh City, Vietnam. Courtesy of D. Scott Smith, MD.

In the 1990s, the World Health Organization (WHO) launched a campaign to eliminate leprosy as a public health problem by 2000. Elimination, as defined by the WHO, was defined as a reduction of patients with leprosy requiring multidrug therapy to fewer than 1 per 10,000 population. This goal was achieved in terms of global prevalence by 2002. As of 2014, none of the 122 countries where leprosy was endemic in 1985 still have prevalence rates of greater than 1 per 10,000 population.[1]

Although multidrug regimens had been used globally to cure nearly 14 million patients with leprosy since 1985, the number of new leprosy cases remained relatively unchanged from 1980 to 2000, ranging from 500,000-700,000 worldwide per year.[2] Between 2001 and 2006, the global incidence of leprosy declined suddenly, largely owing to new case reductions in India. There is debate as to whether this decline in India reflects genuine progress against the disease or an interruption of active case detection.[3]

The goal of the WHO by the end of 2015 is to reduce the rate of new cases with grade-2 disabilities worldwide by at least 35%. This will be carried out by enforcing activities to decrease the delay in diagnosing the disease and actuate treatment with multidrug therapy. This will also have the impact of reducing transmission of the disease in the community.[2] The results of this effort have yet to be published.

Access and delivery of antibiotics continues to be a problem in the most endemic nations. With the precise transmission mechanism of leprosy still unknown and lack of an effective vaccine, leprosy will probably continue to pose an ongoing public health problem in the coming decades.

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Pathophysiology

Leprosy can manifest in different forms, depending on the host response to the organism.

Individuals who have a vigorous cellular immune response to M leprae have the tuberculoid form of the disease that usually involves the skin and peripheral nerves. The number of skin lesions is limited, and they tend to be dry and hypoesthetic. Nerve involvement is usually asymmetric. This form of the disease is also referred to as paucibacillary leprosy because of the low number of bacteria in the skin lesions (ie, < 5 skin lesions, with absence of organisms on smear). Results of skin tests with antigen from killed organisms are positive in these individuals.

Individuals with minimal cellular immune response have the lepromatous form of the disease, which is characterized by extensive skin involvement. Skin lesions are often described as infiltrated nodules and plaques, and nerve involvement tends to be symmetric in distribution. The organism grows best at 27-30°C; therefore, skin lesions tend to develop in the cooler areas of the body, with sparing of the groin, axilla, and scalp. This form of the disease is also referred to as multibacillary leprosy because of the large number of bacteria found in the lesions (ie, >6 lesions, with possible visualization of bacilli on smear). Results of skin tests with antigen from killed organisms are nonreactive.

Patients may also present with features of both categories; however, over time, they usually evolve to one or the other (indeterminate or borderline leprosy). Interestingly, most individuals who are exposed to leprosy never develop the disease.

Classification of leprosy

Leprosy has 2 classification schemas: the 5-category Ridley-Jopling system and the simpler and more commonly used WHO standard.[4]

Ridley-Jopling: Depending on the host response to the organism, leprosy can manifest clinically along a spectrum bounded by the tuberculoid and lepromatous forms of the disease. Most patients fall into the intermediate classifications, which include borderline tuberculoid leprosy, midborderline leprosy, and borderline lepromatous leprosy. The classification of the disease typically changes as it evolves during its progression or management. The Ridley-Jopling system is used globally and forms the basis of clinical studies of leprosy. It may also be more useful in guiding treatment regimens and assessing risk of acute complications. Physical findings in each subtype are presented in the Clinical section.

​According to the WHO, in an endemic area, an individual is considered to have leprosy if he or she shows either of the two following signs:[4]

  • A skin lesion consistent with leprosy and definite sensory loss, with or without thickened nerves
  • Positive skin smears
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Epidemiology

Frequency

United States

In 2014, according to the U.S. Department of Health and Human Services, 175 new cases of leprosy were detected in the United States.[5]

Eighty-five percent of leprosy cases in the United States are found in immigrants,[6] although endemic foci exist in parts of Louisiana, Florida, and Texas along the Gulf of Mexico; in Mexican and Asian California populations; and in Spanish Americans in New York City.

Some cases among native US citizens can be accounted for by exposure to leprosy overseas. Some cases can be attributed to a contact with a known case of leprosy or exposure to infected armadillos.

Based on genetic analysis studies, wild armadillos and many patients with leprosy in the southern United States are infected with the same strain of M leprae.[7] Leprosy may be a zoonosis in the southern United States because armadillos are a large reservoir for this disease.

Nonetheless, history of exposure cannot be verified in many patients.[8]

International

According to WHO figures and as reported by 130 countries, the global annual detection rates have declined from 2004-2010, when 407,791 and 228,474 new cases were reported, respectively (see the images below). The prevalence registered worldwide at the beginning of 2010 was 192,246 cases. Of the new cases, 95% were detected worldwide during 2010 in the following countries: Angola, Bangladesh, Brazil, China, Democratic Republic of the Congo, India, Ethiopia, Indonesia, Madagascar, Mozambique, Myanmar, Nepal, Nigeria, Philippines, Sri Lanka, Sudan, and United Republic of Tanzania.[2] These countries still exhibit pockets of high endemicity.

Leprosy prevalence rates, 2014. Courtesy of WHO, L Leprosy prevalence rates, 2014. Courtesy of WHO, Leprosy: Global situation, http://www.who.int/lep/situation/en/, accessed April 28, 2016.

Mortality/Morbidity

Leprosy is rarely fatal, and the primary consequence of infection is nerve impairment and debilitating sequelae. According to one study, 33-56% of newly diagnosed patients already displayed signs of impaired nerve function.[9] According to estimates, 3 million people who have completed multidrug therapy for leprosy have sustained disability due to nerve damage. Although both lepromatous leprosy and tuberculoid leprosy involve the skin and peripheral nerves, tuberculoid leprosy has more severe manifestations. Nerve involvement results in loss of sensory and motor function, which may lead to frequent trauma and amputation. The ulnar nerve is most commonly involved.

Damage in the following nerves is associated with characteristic impairments in leprosy:

  • Ulnar and median - Clawed hand
  • Posterior tibial - Plantar insensitivity and clawed toes
  • Common peroneal - Foot drop
  • Radial cutaneous, facial, and greater auricular nerves (may also be involved; as seen in the image below)
    Patient with facial nerve palsy and contractures o Patient with facial nerve palsy and contractures of the hand. Daloa, Ivory Coast. Courtesy of D. Scott Smith, MD.

Infiltration by bacteria may lead to destruction of nasal cartilage (lepromatous leprosy), ocular involvement, and diffuse thickening of the skin. Advanced cases of leprosy involve the loss of eyebrows and lashes, but these deformities are less common today.

Worldwide, leprosy is considered the most common cause of crippling of the hand, which is caused by ulnar nerve involvement.[10] Peroneal nerve involvement can lead to foot drop, posterior tibial nerve involvement, and clawed toes.

Race

Leprosy was once endemic worldwide, and no racial predilection is known. In the late 1800s, the incidence of leprosy in northern Europe and North America dropped dramatically, and the disease is now reported primarily in tropical areas.

Sex

Leprosy is generally more common in males than in females, with a male-to-female ratio of 2:1. In some areas in Africa, the prevalence of leprosy among females is equal to or greater than that in males.[11]

Age

Leprosy can occur at any age, but, in developing countries, the age-specific incidence of leprosy peaks in children younger than 10 years, who account for 20% of leprosy cases. Leprosy is very rare in infants; however, they are at a relatively high risk of acquiring leprosy from the mother, especially in cases of lepromatous leprosy or midborderline leprosy.

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Contributor Information and Disclosures
Author

Darvin Scott Smith, MD, MSc, DTM&H Adjunct Associate Clinical Professor, Department of Microbiology and Immunology, Stanford University School of Medicine; Chief of Infectious Diseases and Geographic Medicine, Department of Internal Medicine, Kaiser Redwood City Hospital

Darvin Scott Smith, MD, MSc, DTM&H is a member of the following medical societies: American Medical Association, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, International Society of Travel Medicine

Disclosure: Nothing to disclose.

Coauthor(s)

Emily Anderson Kelly Stanford University

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Charles V Sanders, MD Edgar Hull Professor and Chairman, Department of Internal Medicine, Professor of Microbiology, Immunology and Parasitology, Louisiana State University School of Medicine at New Orleans; Medical Director, Medicine Hospital Center, Charity Hospital and Medical Center of Louisiana at New Orleans; Consulting Staff, Ochsner Medical Center

Charles V Sanders, MD is a member of the following medical societies: American College of Physicians, Alliance for the Prudent Use of Antibiotics, The Foundation for AIDS Research, Southern Society for Clinical Investigation, Southwestern Association of Clinical Microbiology, Association of Professors of Medicine, Association for Professionals in Infection Control and Epidemiology, American Clinical and Climatological Association, Infectious Disease Society for Obstetrics and Gynecology, Orleans Parish Medical Society, Southeastern Clinical Club, American Association for the Advancement of Science, Alpha Omega Alpha, American Association of University Professors, American Association for Physician Leadership, American Federation for Medical Research, American Geriatrics Society, American Lung Association, American Medical Association, American Society for Microbiology, American Thoracic Society, American Venereal Disease Association, Association of American Medical Colleges, Association of American Physicians, Infectious Diseases Society of America, Louisiana State Medical Society, Royal Society of Medicine, Sigma Xi, Society of General Internal Medicine, Southern Medical Association

Disclosure: Received royalty from Baxter International for other.

Chief Editor

Michael Stuart Bronze, MD David Ross Boyd Professor and Chairman, Department of Medicine, Stewart G Wolf Endowed Chair in Internal Medicine, Department of Medicine, University of Oklahoma Health Science Center; Master of the American College of Physicians; Fellow, Infectious Diseases Society of America

Michael Stuart Bronze, MD is a member of the following medical societies: Alpha Omega Alpha, American Medical Association, Oklahoma State Medical Association, Southern Society for Clinical Investigation, Association of Professors of Medicine, American College of Physicians, Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Additional Contributors

Fred A Lopez, MD Associate Professor and Vice Chair, Department of Medicine, Assistant Dean for Student Affairs, Louisiana State University School of Medicine

Fred A Lopez, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians-American Society of Internal Medicine, Infectious Diseases Society of America, Louisiana State Medical Society

Disclosure: Nothing to disclose.

Shwetha Ravindranath Katta, MD JJM Medical College, Davangere, India

Disclosure: Nothing to disclose.

Acknowledgements

Tara Ramachandra, MD Stanford University School of Medicine

Disclosure: Nothing to disclose.

References
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  2. Scollard DM, Adams LB, Gillis TP, Krahenbuhl JL, Truman RW, Williams DL. The continuing challenges of leprosy. Clin Microbiol Rev. 2006 Apr. 19(2):338-81. [Medline]. [Full Text].

  3. Schreuder PAM, Noto S, Richardus JH. Epidemiologic trends of leprosy for the 21st century. Clinics in Dermatology. 2015 Nov 04. Volume 34, Issue 1:24-31.

  4. The World Health Organization. Diagnosis of Leprosy. Leprosy Elimination. Available at http://www.who.int/lep/diagnosis/en/. Accessed: April 15, 2016.

  5. U.S. Department of Health and Human Services. National Hansen's Disease (Leprosy) Program. Health Resources and Services Administration. Available at http://www.hrsa.gov/hansensdisease/. Accessed: March 23, 2016.

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  7. Truman RW, Singh P, Sharma R, et al. Probable zoonotic leprosy in the southern United States. N Engl J Med. 2011 Apr 28. 364(17):1626-33. [Medline].

  8. Joyce MP, Scollard DM. Leprosy (Hansen's Disease). Conn's Current Therapy. 2004. 100-105.

  9. Ustianowski AP, Lockwood DN. Leprosy: current diagnostic and treatment approaches. Curr Opin Infect Dis. 2003 Oct. 16(5):421-7. [Medline].

  10. Anderson GA. The surgical management of deformities of the hand in leprosy. J Bone Joint Surg Br. 2006 Mar. 88(3):290-4. [Medline].

  11. The World Health Organization. Transmission of Leprosy. Leprosy Elimination. Available at http://www.who.int/lep/transmission/en/. Accessed: April 15, 2016.

  12. Walker SL, Lockwood DN. Leprosy. Clin Dermatol. 2007 Mar-Apr. 25(2):165-72. [Medline].

  13. Anderson H, Stryjewska B, Boyanton BL, et al. Hansen disease in the United States in the 21st century: a review of the literature. Arch Pathol Lab Med. 2007 Jun. 131(6):982-6. [Medline].

  14. Martinez AN, Talhari C, Moraes MO, Talhari S. PCR-based techniques for leprosy diagnosis: from the laboratory to the clinic. PLoS Negl Trop Dis. 2014 Apr. 8 (4):e2655. [Medline].

  15. Health and Human Resources Administration. Hansens Disease. National Hansen's Disease (Leprosy) Clinical Center. Available at http://www.hrsa.gov/hansensdisease/clinicalcenter.html. Accessed: April 15, 2016.

  16. Van Veen NH, Nicholls PG, Smith WC, Richardus JH. Corticosteroids for treating nerve damage in leprosy. Cochrane Database Syst Rev. 2007 Apr 18. CD005491. [Medline].

  17. Kai M, Nguyen Phuc NH, et al. Analysis of Drug-Resistant Strains of Mycobacterium leprae in an Endemic Area of Vietnam. Clin Infect Dis. Mar 2011;52(5):e127-32.

  18. Singh P, Busso P, Paniz-Mondolfi A, et al. Molecular Drug Susceptibility Testing and Genotyping of Mycobacterium leprae Strains from South America. Antimicrob Agents Chemother. 2011 Jun. 55(6):2971-3. [Medline]. [Full Text].

  19. Bakker MI, Hatta M, Kwenang A, et al. Risk factors for developing leprosy--a population-based cohort study in Indonesia. Lepr Rev. 2006 Mar. 77(1):48-61. [Medline].

  20. Britton WJ, Lockwood DN. Leprosy. Lancet. 2004 Apr 10. 363(9416):1209-19. [Medline].

  21. Deps PD, Guedes BV, Bucker Filho J, Andreatta MK, Marcari RS, Rodrigues LC. Characteristics of known leprosy contact in a high endemic area in Brazil. Lepr Rev. 2006 Mar. 77(1):34-40. [Medline].

  22. Jacobson RR, Krahenbuhl JL, Yoder L. Overview of Leprosy. UpToDate. 2006.

  23. Leprosy. World Health Organization. Available at www.who.org.

  24. Moschella SL. An update on the diagnosis and treatment of leprosy. J Am Acad Dermatol. 2004 Sep. 51(3):417-26. [Medline].

  25. National Hansen's Disease (Leprosy) Program. U.S. Department of Health and Human Services. Available at http://www.hrsa.gov/hansensdisease/index.html. Accessed: July 21, 2014.

  26. Rao PS, Sugamaran DS, Richard J, et al. Multi-centre, double blind, randomized trial of three steroid regimens in the treatment of type-1 reactions in leprosy. Lepr Rev. 2006 Mar. 77(1):25-33. [Medline].

  27. Sridharan R, Lorenzo N, Narasimhan L. Leprosy. Medscape Reference. 2005.

  28. van Beers SM, Hatta M, Klatser PR. Patient contact is the major determinant in incident leprosy: implications for future control. Int J Lepr Other Mycobact Dis. 1999 Jun. 67(2):119-28. [Medline].

 
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Hands with Z-thumbs, clawing, contractures, and shortening of fingers due to repetitive injury and healing. Ho Chi Minh City, Vietnam. Courtesy of D. Scott Smith, MD.
Patient with facial nerve palsy and contractures of the hand. Daloa, Ivory Coast. Courtesy of D. Scott Smith, MD.
Chronic insensate patch due to leprosy infection. Ho Chi Minh City, Vietnam. Courtesy of D. Scott Smith, MD.
Characteristic clawed hand deformity caused by ulnar involvement in leprosy. Daloa, Ivory Coast. Courtesy of D. Scott Smith, MD.
Chronic nonhealing ulcer at the metatarsal head resulting from loss of sensation in the feet. Karigiri, Tamil Nadu, India. Courtesy of Tara Ramachandra.
Multiple flat hypopigmented lesions on shoulder and neck, suggestive of multibacillary leprosy. Note ulceration of hypothenar area of hand, indicative of ulnar neuropathy. Redwood City, California, United States. Courtesy of D. Scott Smith, MD.
Man with advanced deformities caused by unmanaged leprosy. Keratitis, loss of eyebrow, thickened skin, and typical hand impairments. Ho Chi Minh City, Vietnam. Courtesy of D. Scott Smith, MD.
Histopathology of leprosy: Large numbers of acid-fast bacilli (in clusters) in histiocytes and within nerves. Fite-Faraco stain 500 X. Courtesy of Tara Ramachandra and D. Scott Smith, MD.
Patient with multibacillary leprosy showing subsequent erythema nodosum leprosum reaction. Santa Clara, California. Courtesy of D. Scott Smith, MD.
Patient with erythema nodosum leprosum type 2 reaction several weeks after initiation of drug therapy. This photograph was taken after tendon release. Redwood City, California. Courtesy of D. Scott Smith, MD.
Increased pigmentation on the face due to clofazimine therapy. Courtesy of D. Scott Smith, MD.
WHO Multidrug Therapy Regimens. Courtesy of WHO, Leprosy Elimination, http://www.who.int/lep/mdt/en/, accessed April 15, 2016.
Leprosy prevalence rates, 2014. Courtesy of WHO, Leprosy: Global situation, http://www.who.int/lep/situation/en/, accessed April 28, 2016.
Table 1. Multidrug Therapy Plan Recommended by the WHO
Type of Leprosy Daily, Self-Administered Monthly Supervised Months of Treatment
Paucibacillary Dapsone 100 mg Rifampicin 600 mg 6
Single-lesion paucibacillary Rifampicin 600 mg,



Ofloxacin 400 mg,



Minocycline 100 mg



N/A Single dose
Multibacillary Dapsone 100 mg,



Clofazimine 50 mg



Rifampicin 600 mg,



Clofazimine 300 mg 



12
Pediatric Dapsone 2 mg/kg,



Clofazimine 1 mg/kg



Rifampicin 10 mg/kg,



Clofazimine 6 mg/kg



Same as in adults
Table 2. US Recommendations for Multidrug Therapy [15]
Type of Leprosy Daily, Self-Administered Monthly Supervised Months of Treatment
Paucibacillary Dapsone 100 mg,



Rifampicin 600 mg



N/A 12
Single-lesion paucibacillary Dapsone 100 mg,



Rifampicin 600 mg



N/A 12
Multibacillary Dapsone 100 mg,



Rifampicin 600 mg,



Clofazimine 50 mg



N/A 24
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