Leprosy overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]
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, microbiologic 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
Due to clinical manifestations such as skin lesions, nodules, plaques paresthesias and nerve pain, leprosy should be distinguished from conditions with similar presentations, such as autoimmune diseases, SLE, parasitic infections, vitiligo or cutaneous tuberculosis.
Epidemiology and Demographics
Current prevalence rate of leprosy per 100,000 is 3.7. The disease is more prevalent in endemic areas, which represent a potential source of spread of the disease to the rest of the world.
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 may lead to severe complications if not diagnosed and treated early, which will affect the prognosis.
Diagnosis
Diagnostic Criteria
For the diagnosis of leprosy at least 1 of 3 criteria should be present: loss of sensation of a hipopigmented skin patch, a thickened peripheral nerve concomitantly with weakness or loss of sensation of the area, and/or confirmation of mycobacterium leprae in the skin smear.
History and Symptoms
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 or burns. Elements such as travel history, social contacts and concomitant clinical manifestations are also essential to reach a correct diagnosis.
Physical Examination
Physical examination will depend on the class of leprosy in each patient and may include findings such as hypopigmented skin lesions, usually macular or papular, thickened dermis, loss of sensation or 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 may lead to fractures.
Other Imaging Findings
No other imaging studies are indicated for the diagnosis of leprosy.
Other Diagnostic Studies
Studies such as biopsy of skin lesions and skin smear tests have an important contribution for the diagnosis of leprosy in patients whose clinical examination is suspicious of the disease.
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.
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
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
It is not possible to know if a contact with a patient with leprosy will lead to the development of leprosy until first symptoms appear, hence no secondary prevention is available.
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 necessary.[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
To further decrease the prevalence leprosy in endemic regions, new research studies are required to improve the current concepts of diagnosis and therapy of leprosy, bringing the same level of treatment to every area in the world.
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.
- ↑ "Enhanced global strategy for further reducing the disease burden due to leprosy (2011-2015)" (PDF).