eMedicine Specialties > Pediatrics: General Medicine > Infectious Disease
Leprosy
Updated: May 22, 2009
Introduction
Background
Leprosy is a chronic granulomatous disease caused by infection with Mycobacterium leprae. This disease, which was described almost 3000 years ago, is still associated with stigma. M leprae was first described in 1873 when Gerhard Armauer Henrik Hansen discovered it while examining lymph nodes and other tissues obtained from patients with leprosy. Although significant progress was made during the 20th century in the treatment and eradication of this disease, the World Health Organization (WHO) estimates that the worldwide prevalence is still close to 12 million cases.
Pathophysiology
The exact mechanism of M leprae transmission remains unknown; however, direct human-to-human contact, contact with respiratory secretions from infected individuals, and vertical transmission have been considered the most likely routes of transmission. Most pathophysiological changes observed in leprosy are caused by the ability of M leprae to survive in macrophage cells. Although the incubation period of M leprae can be several decades, it generally averages 5-7 years.1
Frequency
United States
Most observed infections are acquired abroad. In California, recent cases of leprosy have been reported in persons who have emigrated from Mexico and Southeast Asia. Leprosy is also occasionally reported in Texas and Louisiana. In 2002, 133 cases of leprosy were reported in the United States. In 2006, approximately 6,500 persons with leprosy were living in the United States.2
International
The WHO has estimated the global prevalence of leprosy to be 10-12 million cases, with most reported in Africa and Asia, particularly in the Indian subcontinent. The worldwide incidence rate is 2 cases per 10,000 population. In some areas, as many as 10% of cases develop in children younger than 15 years, among whom paucibacillary forms are more frequent.3
Race
Leprosy has no known racial predilection. Rather than race, lower socioeconomic status has traditionally been considered a risk factor for leprosy in endemic areas.
Sex
The male-to-female ratio is 2:1 to 3:1.
Age
Although this infection is rarely reported in infancy, it can affect all ages. In areas of high prevalence, leprosy among children represents 7-10% of new cases.3
Clinical
History
- Patients with leprosy are usually native to or have emigrated from endemic areas.
- Because of the prolonged incubation period, which averages 5 years, most cases are not diagnosed until several years after initial exposure.
- Neuromuscular symptoms associated with this disease are occasionally the first to be observed. Patients may also present with a history of chronic nasal discharge, which is frequently observed in individuals with lepromatous leprosy who have upper airway compromise.
Physical
- The hallmark clinical findings in leprosy are hypopigmented skin lesions with loss of sensation. These lesions are observed more frequently in the cooler areas of the body, such as the nose and earlobes.
Infiltration of the ear lobes in a patient with lepromatous leprosy.
- Hypoesthesia is the clinical manifestation of peripheral nerve involvement and is present in as many as 70% of children with this condition.
- Depending on the number of lesions and the number of bacillus observed on the lesion's smear, leprosy can be classified into the following 3 groups:
- Borderline leprosy: This is characterized by the presence of single or multiple skin lesions with a raised central area.
- Paucibacillary (tuberculoid) leprosy
- Tuberculoid leprosy presents with one or few (usually <5) hypopigmented and hypoesthetic lesions. Sensory loss is frequently observed around the lesions
- Patients with tuberculoid leprosy have a characteristic normal cell-mediated response to M leprae antigens.
- Multibacillary (lepromatous) leprosy
- Lepromatoid leprosy usually presents with multiple (>5) poorly defined, hypopigmented or erythematous lesions associated with hypoesthesia. It is also associated with the presence of papules, macules, and nodular lesions. Necrotizing erythema nodosum has occasionally been reported in children.
- Patients with advanced lepromatous leprosy may present with loss of eyelashes or eyebrows and nasal septum perforation. The constellation of disfiguring facial features associated with this disease is named leonine facies.
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).
- The peripheral neuropathy observed in lepromatous leprosy causes muscle weakness and atrophy and has been associated with clawhands and foot drops.
- Other clinical manifestations of lepromatous leprosy include corneal opacifications, keratitis, iritis, testicular atrophy, and kidney disease resulting in renal failure.
- Patients with lepromatous leprosy present with characteristically abnormal cell-mediated responses to M leprae antigens.4
- Erythema nodosum leprosum (ENL) is a condition observed in patients with borderline and lepromatous leprosy. It is usually associated with neuritis, fever, and arthralgias. The development of ENL has been suggested to be caused by the presence of immune complexes.5
- The development of nonhealing ulcers in the lower extremities of patients with lepromatous leprosy secondary to arthritis is known as the Lucio phenomenon. These ulcerations are more common in individuals of Latin American descent and are associated with a high mortality rate.
- Neuropathic pain can be a sequelae of multibacillary leprosy that can present more than 10 years after completion of therapy.6
- Leprosy immune reconstitution disease can develop among patients co-infected with HIV who undergo treatment with highly active antiretroviral therapy.7
Causes
- Leprosy is a chronic granulomatous disease caused by infection with M leprae.
More on Leprosy |
 Overview: Leprosy |
| Differential Diagnoses & Workup: Leprosy |
| Treatment & Medication: Leprosy |
| Follow-up: Leprosy |
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| References |
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References
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Further Reading
Keywords
leprosy, Hansen's disease, Hansen disease, Mycobacterium leprae, M leprae, borderline leprosy, paucibacillary leprosy, tuberculoid leprosy, multibacillary leprosy, lepromatous leprosy, erythema nodosum leprosum, ENL, Lucio phenomenon, Lucio's phenomenon, lazarine leprosy, chronic granulomatous disease, , hypoesthesia, necrotizing erythema nodosum, leonine facies
