Leprosy overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Leprosy is a chronic infectious disease caused by the bacterium Mycobacterium leprae.[1] Leprosy is primarily a granulomatous disease of the peripheral nerves and mucosa of the upper respiratory tract; skin lesions are the primary external symptom. Left untreated, leprosy can be progressive, causing permanent damage to the skin, nerves, limbs, and eyes.
Historical Perspective
Mycobacterium leprae, the causative agent of leprosy, was discovered by G. H. Armauer Hansen in Norway in 1873, making it the first bacterium to be identified as causing disease in man.[2][3] The importance of the nasal mucosa was recognized as early as 1898 by Schäffer, particularly that of the ulcerated mucosa. Historically, individuals with Hansen's disease have been known as lepers, however, this term is falling into disuse as a result of the diminishing number of leprosy patients and the pejorative connotations of the term. The term most widely accepted among people and agencies working in the field of Hansen's disease is 'people affected by Hansen's disease.
Classification
The Ridley Jopling classification and the WHO classification are the two most widely used systems to classify Leprosy. These classification systems are based on clinical, microbiological and histopathological features, and are used to determine the patient's prognosis and the treatment regimen.[4][5][6]
Pathophysiology
Leprosy is a chronic disease, whose clinical features depend on the immune response of the host towards the infection. Once the bacterial cells penetrate and multiply within host cells, predominately skin and peripheral nerve cells, the immune system develops a responses against those infected cells, thereby justifying some of the symptoms. There have identified several gene SNPs related to susceptibility to the disease, which has microscopic and gross manifestations.
Causes
Mycobacterium leprae is a gram-positive obligate intracellular, acid-fast bacillus, responsible for the development of leprosy, or Hansen's disease. This organism has a very slow growth and affects particularly colder parts of the body, such as the skin, superficial nerves and upper respiratory mucous membranes. Although a route of transmission has not been absolutely defined yet, studies are pointing to a colonization of the dermis and respiratory mucosa of the infected patients, with the respiratory system also as the entry port. It is an uncommon bacteria, since it has only been noticed to infect and grown in some species of primates and in the nine-banded armadillo.[6]
Differential Diagnosis
Leprosy is has a very important skin component, with manifestations such as skin lesions, nodules, plaques and thickened dermis, Thise manifestations may be present in other conditions, from which leprosy should then be distinguished. These may include autoimmune diseases, such as vitiligo and SLE, parasitic infections, such as dermatophyte or more generalized infections, such as cutaneous tuberculosis.
Epidemiology and Demographics
In 1990, the WHO defined a goal of eliminating leprosy as a public health issue within 10 years. Between the years of 1985 and 2010, the number of registered cases of leprosy fell from 5.4 million to 244,796, with prevalence rate per 10,000 falling from 21,1 to 0.37. However this prevalence is very variable according to the region, since most reported cases come from developing countries, such as India, Brazil and Indonesia. Efforts have been made to decrease the number of cases in endemic areas and to avoid transmission of the disease to other parts of the world, since international travel represents an important vehicle of the bacteria into other parts of the globe. This transmission has such impact that among the cases reported annually in the United States, 75% occur in emigrants.[7]
Risk Factors
Close contacts of patients with untreated, active multibacillary disease are at highest risk of acquiring leprosy. Children are more susceptible than adults to contracting the disease.
Natural History, Complications and Prognosis
Leprosy, when not diagnosed early and treated appropriately may lead to severe complications, such as severe nerve damage, blindness, contractures and Lucio phenomenon. The prognosis will depend on how early the diagnosis is reached and how soon the multidrug therapy is started.
Diagnosis
Diagnostic Criteria
Leprosy is a disease with very different clinical presentations, depending on the immune response provided by the host. Therefore it is important to consider the different conditions that may mimic leprosy's presentation, particularly since the diagnosis of leprosy has a very serious psychological and social impact in someone's life. To minimize the risk of reaching an erroneous diagnosis and inflicting stress and concern in the patient, criteria were developed to guide the diagnosis, which should only be communicated to the patient when a reasonable degree of certainty is present.
History and Symptoms
Despite the considerable decrease in the incidence of leprosy in recent years, after the preventive and treatment measures applied by the WHO, there are still endemic areas of this disease, particularly in developing countries. Accordingly, the diagnostic procedures and the time to reach a correct diagnosis will depend on the area of the world it occurs. The diagnosis of leprosy should be considered when there is history of skin lesions that do not respond to treatment for more common conditions or when in presence of sensory loss with concomitant trauma lesions or burns. Elements such as travel history, social contacts and concomitant clinical manifestations are also essential in reaching a correct diagnosis, which contributes to a decrease of morbidity of this condition.
Physical Examination
Leprosy is a disease that may present with different clinical manifestations throughout its course, and among different patients, depending on the response of the immune system. Therefore, physical findings will depend on the class of leprosy on that particular patient. Common physical findings include hypopigmented skin lesions, usually macular or papular, thickened dermis, loss of sensation and peripheral nerve thickening, with common evolvement of the nasal mucosa.
Laboratory Findings
No laboratory tests are available for the diagnosis of leprosy.
X Ray
Osteoporosis is a common finding in leprosy patients, which along with the decreased sensitivity and pain experienced by these individuals, make evidence of fractures on the X-ray, a common finding.
Other Imaging Findings
No other imaging studies are indicated for the diagnosis of leprosy.
Other Diagnostic Studies
Although there are no laboratory studies to help in the diagnosis of leprosy, other studies such as biopsy of skin lesions and skin smear tests have an important contribution for the diagnosis of leprosy in patients, whose diagnosis is suspected from the clinical presentation.
Treatment
Medical Therapy
The medical treatment of leprosy is made with a multiple drug regimen, that must be followed rigorously during a long period of time, 6 to 12 months, depending on the class of disease. This drug regimen includes 2 to 3 different drugs, in order to minimize the risk of resistance by the bacillus, and its administration should be monitored closely by health care personnel to insure adherence to the treatment.
Surgery
Although surgery is not indicated in the treatment of leprosy, it may treat, or decrease the impact, of some of the complications that may arise from the disease.
Primary prevention
Unfortunately there are still endemic regions in the world, where people are deeply affected by leprosy, and that due to international travels, threaten to be be a source of the bacteria for the entire world. Although an effective treatment regimen is available, primary prevention measures play a dominant role in minimizing the impact of the disease. Immuno and chemoprophylaxis of leprosy and other infectious diseases are fundamental measures to prevent infection by the Mycobacterium leprae, however, adequate education of the populations also has a great impact in minimizing this risk.
Secondary Prevention
Unfortunately today it is not available a test to identify if a person was infected by [Mycobacterium leprae]] until the first symptoms start to appear. However, primary and tertiary prevention are two ways of preventing being infected with the disease, as well as minimizing damage caused in patients with this condition.
Tertiary prevention
After leprosy has been diagnosed and treatment has been initiated, other measures may be taken, in order to minimize further damage to the patient. These include: education of the patient and family members to monitor and treat skin ulcers and other lesions, primary care facilities to provide help to the populations and to direct patients to a specialist, whenever needed.[7]
Cost-effectiveness of Therapy
After the results of the campaign of the WHO to eradicate leprosy, the treatment of this disease may be considered cost-effective.
Future or Investigational Therapies
In the last few years the WHO has implemented measures and treatment approaches that were able to considerably decrease the incidence of leprosy on a worldwide level. However, there are still endemic areas that need to see these and further measures implemented, in order to minimize the impact of this disease. For this to be accomplished, new research studies are required to help improve the current concepts of diagnosis and therapy of leprosy, bringing the same level of treatment to every area in the world, particularly endemic regions in developing countries.
References
- ↑ Sasaki S, Takeshita F, Okuda K, Ishii N (2001). "Mycobacterium leprae and leprosy: a compendium". Microbiol Immunol. 45 (11): 729–36. PMID 11791665.
- ↑ Hansen GHA (1874). "Undersøgelser Angående Spedalskhedens Årsager (Investigations concerning the etiology of leprosy)". Norsk Mag. Laegervidenskaben (in Norwegian). 4: pp. 1–88.
- ↑ Irgens L (2002). "The discovery of the leprosy bacillus". Tidsskr Nor Laegeforen. 122 (7): 708–9. PMID 11998735.
- ↑ Walker, Stephen L.; Lockwood, Dina N.J. (2007). "Leprosy". Clinics in Dermatology. 25 (2): 165–172. doi:10.1016/j.clindermatol.2006.05.012. ISSN 0738-081X.
- ↑ Eichelmann, K.; González González, S.E.; Salas-Alanis, J.C.; Ocampo-Candiani, J. (2013). "Leprosy. An Update: Definition, Pathogenesis, Classification, Diagnosis, and Treatment". Actas Dermo-Sifiliográficas (English Edition). 104 (7): 554–563. doi:10.1016/j.adengl.2012.03.028. ISSN 1578-2190.
- ↑ 6.0 6.1 Bhat, Ramesh Marne; Prakash, Chaitra (2012). "Leprosy: An Overview of Pathophysiology". Interdisciplinary Perspectives on Infectious Diseases. 2012: 1–6. doi:10.1155/2012/181089. ISSN 1687-708X.
- ↑ 7.0 7.1 "Leprosy: global situation".