Leprosy, also called Hansen's disease, is a chronic infectious disease that primarily affects the skin, the peripheral nerves, the mucosa of the upper respiratory tract, and the eyes. Leprosy can lead to progressive permanent damage of these structures, and the resulting devastating disfigurement and disability has led to the historical social stigma and isolation (leper colonies) of those affected by the disease.
Leprosy is a curable disease with the use of multidrug therapy (MDT). In 1991, the World Health Assembly passed a resolution to eliminate leprosy as a public-health problem by the year 2000. With assistance from the World Health Organization (WHO), MDT has been distributed free to all patients with leprosy since 1995. Though leprosy is still endemic in a few developing countries (primarily in the tropics), there has been a dramatic worldwide decrease in the prevalence of the disease due to this successful public-health initiative.
The signs and symptoms of leprosy can vary depending on the individual's immune response to M. leprae. The WHO classification system uses clinical manifestations (the number of skinlesions and nerve involvement) as well as skin smear results to distinguish between paucibacillary leprosy and multibacillary leprosy forms of the disease.
The two major WHO classifications are paucibacillary and multibacillary leprosy. However, within the WHO's simplified classification there can be a fairly wide range of patient presentations.
- Negative skin smear results at all sites with two to five skin lesions or paucibacillary single lesion leprosy with negative skin smear results at all sites within a single lesion.
- Positive skin smear results at any site with more than five skin lesions.
The Ridley-Jopling classification is another classification system that is used globally in evaluating patients in clinical studies and contains six different classifications of leprosy that further define the patient's severity of symptoms and disease progression.
The signs and symptoms of leprosy may vary with the form of the disease and include the following:
- flat or raised skin lesions or nodules, often less pigmented than the surrounding skin, though they may reddish or copper colored;
- single or multiple skin lesions that are often found on cooler parts of the body such as the face, buttocks and extremities;
- thickening of the skin and peripheral nerves;
- ulcerations of the skin;
- peripheral nerve involvement leading to loss of sensation;
- peripheral nerve involvement leading to muscle weakness (for example, clawed hand deformities, contractures, and foot drop);
- testicular involvement leading to sexual dysfunction or sterility;
- eye involvement including eye pain, eye redness, inability to close the eyelids,corneal ulcers and blindness;
- loss of eyebrows and eyelashes;
- destruction of the nasal cartilage.
Leprosy is an acquired infectious disease that can affect individuals of all ages. It is caused by the rod-shaped bacteria Mycobacterium leprae, which was discovered in 1873 by G.A. Hansen.
- Because the bacterium multiplies very slowly, the signs and symptoms of leprosy may not develop until much later after exposure to M. leprae (ranging from several weeks to 30 years or more).
- Though humans are the major reservoir and host for infection with M. leprae, other animals such as armadillos, chimpanzees, and mangabey monkeys also serve as reservoirs of infection.
- Leprosy is thought to be transmitted via droplets from the nose and mouth during close prolonged contact with affected individuals, though the exact route of transmission has yet to be proven definitively.
- Not all individuals infected with M. leprae will go on to develop leprosy, because only 5%-10% of the population is thought to be susceptible to the infection because of immunological reasons.
The majority of cases (mainly clinically diagnosed) are treated with antibiotics. The recommended antibiotics, their dosages, and length of time of administration are based on the form or classification of the disease and whether or not the patient is supervised by a medical professional. In general, paucibacillary leprosy is treated with two antibiotics, dapsone and rifampicin, while multibacillary leprosy is treated with the same two plus a third antibiotic, clofazimine. Usually, the antibiotics are given for at least six to 12 months or more.
Antibiotics can treat paucibacillary leprosy with little or no residual effects on the patient. Multibacillary leprosy can be kept from advancing, and living M. leprae can be essentially eliminated from the person by antibiotics, but the damage done before antibiotics are administered is usually not reversible.
Recently, the WHO suggested that single-dose treatment of patients with only one skin lesion with rifampicin, minocycline (Minocin), or ofloxacin (Floxin) is effective. Studies of other antibiotics are ongoing. Each patient, depending on the above criteria, has a schedule for their individual treatment, so treatment schedules should be planned by a clinician knowledgeable about that patient's initial diagnostic classification.
The role for surgery in the treatment of leprosy occurs after medical treatment (antibiotics) has been completed with negative skin smears (no detectable acid-fast bacilli) and is often only needed in advanced cases. Surgery is individualized for each patient with the goal to attempt cosmetic improvements and, if possible, to restore limb function and some neural functions that were lost to the disease.
How is leprosy prevented?
Prevention of contact with droplets from nasal and other secretions from patients with untreated M. leprae infection currently is a way recommended to avoid the disease.
Treatment of patients with appropriate antibiotics stops the person from spreading the disease. People who live with individuals who have untreated leprosy are about eight times as likely to develop the disease, because investigators speculate that family members have close proximity to infectious droplets. Leprosy is not hereditary, but recent findings suggest susceptibility to the disease may have a genetic basis.
Many people get exposed to leprosy throughout the world, but the disease in not highly contagious; researchers suggest that over 95% of exposures result in no disease, and further studies suggest that susceptibility may be based, in part, by a person's genetic makeup. In the U.S., there are about 200-300 new cases diagnosed per year, with most coming from exposures during foreign travel.
The majority of worldwide cases are found in the tropics or subtropics (for example, Brazil, India, and Indonesia). The WHO reports about 500,000 to 700,000 new cases per year worldwide, with curing of about 14 million cases since 1985.
There is no commercially available vaccine available to prevent leprosy. However, there are reports of using BCG vaccine, the BCG vaccine along with heat-killed M. leprae organisms, and other preparations that may be protective or help to clear the infection or to shorten treatment. Except for BCG in some countries, these preparations are not readily available.
Animals (chimpanzees, mangabey monkeys, and nine-banded armadillos) rarely transfer M. leprae to humans; nonetheless, handling such animals in the wild is not advised. These animals are a source for endemic infections.