Leprosy

Leprosy or Hansen's disease (HD), is a chronic disease caused by the bacteria Mycobacterium leprae and Mycobacterium lepromatosis. Named after physician Gerhard Armauer Hansen, leprosy is primarily a granulomatous disease of the peripheral nerves and mucosa of the upper respiratory tract; skin lesions are the primary external sign. Left untreated, leprosy can be progressive, causing permanent damage to the skin, nerves, limbs and eyes. Contrary to folklore, leprosy does not cause body parts to fall off, although they can become numb or diseased as a result of infection; infection results in tissue loss, so fingers and toes become shortened and deformed as the cartilage is absorbed into the body.

Although the mode of transmission of Hansen's disease remains uncertain, most investigators think that M. leprae is usually spread from person to person in respiratory droplets. Leprosy is also believed to be spread by armadillos. Leprosy is now known to be neither sexually transmitted nor highly infectious after treatment. Approximately 95% of people are naturally immune and sufferers are no longer infectious after as little as 2 weeks of treatment.

The minimum incubation period reported is as short as a few weeks and this is based on the very occasional occurrence of leprosy among young infants. The maximum incubation period reported is as long as 30 years, or over, as observed among war veterans known to have been exposed for short periods in endemic areas but otherwise living in non-endemic areas. It is generally agreed that the average incubation period is between three and five years.

Leprosy has affected humanity for over 4,000 years, and was well-recognized in the civilizations of ancient China, Egypt, and India. In 1995, the World Health Organization (WHO) estimated that between 2 and 3 million people were permanently disabled because of leprosy at that time. In the past 20 years, 15 million people worldwide have been cured of leprosy.Although the forced quarantine or segregation of patients is unnecessary in places where adequate treatments are available, many leper colonies still remain around the world in countries such as India (where there are still more than 1,000 leper colonies), China,Romania, Egypt, Nepal, Somalia, Liberia, Vietnam,and Japan. Leprosy was once believed to be highly contagious and was treated with mercury—all of which applied to syphilis which was first described in 1530. It is now thought that many early cases of leprosy could have been syphilis.

The age-old social stigma, in other words, leprosy stigma associated with the advanced form of leprosy lingers in many areas, and remains a major obstacle to self-reporting and early treatment. Effective treatment for leprosy appeared in the late 1930s with the introduction of dapsone and its derivatives. Leprosy bacilli resistant to dapsone soon evolved and, due to overuse of dapsone, became widespread. It was not until the introduction of multidrug therapy (MDT) in the early 1980s that the disease could be diagnosed and treated successfully within the community.

MDT for multibacillary leprosy consists of rifampicin, dapsone, and clofazimine taken over 12 months. Dosages adjusted appropriately for children and adults are available in all Primary Health Centres in the form of blister packages. Single dose MDT for single lesion leprosy consists of rifampicin, ofloxacin, and minocycline. The move towards single dose treatment strategies has reduced the prevalence of disease in some regions since prevalence is dependent on duration of treatment.

World Leprosy Day was created to draw awareness to leprosy and its sufferers.

Classification

There are several different approaches for classifying leprosy, however, parallels exist.

The World Health Organization system distinguishes "paucibacillary" and "multibacillary" based upon the proliferation of bacteria ("pauci-" refers to a low quantity.)

The SHAY scale provides five gradations.

The ICD-10, though developed by the WHO, uses Ridley-Jopling and not the WHO system. It also adds an indeterminate ("I") entry.

In MeSH, three groupings are used.

Signs and symptoms

Skin lesions are the primary external sign. Left untreated, leprosy can be progressive, causing permanent damage to the skin, nerves, limbs and eyes. Contrary to folklore, leprosy does not cause body parts to fall off but they can become numb or diseased as a result of the disease.

Diagnosis

Diagnosis in the U.S. is often delayed because health care providers are unaware of leprosy and its symptoms. Early diagnosis and treatment prevents nerve involvement, the hallmark of leprosy, and the disability it causes.

There are many kinds of leprosy but there are common symptoms. These include runny nose, dry scalp, eye problems, and muscle weakness.

Risk factors

At highest risk are those living in endemic areas with poor conditions such as inadequate bedding, contaminated water and insufficient diet, or other diseases (such as HIV) that compromise immune function. Recent research suggests that there is a defect in cell-mediated immunity that causes susceptibility to the disease. Less than ten percent of the world's population is actually capable of acquiring the disease. The region of DNA responsible for this variability is also involved in Parkinson disease, giving rise to current speculation that the two disorders may be linked in some way at the biochemical level. In early 2003, an international team of scientists conducted a genome scan in Vietnamese multiplex leprosy families and found that susceptibility to leprosy was significantly linked to region q25 on the long arm of chromosome 6. Further confirmation of the chromosome 6 locus was provided by high-resolution linkage mapping in simplex leprosy families. Now, in a continuation of these findings, the team has pinpointed the chromosome 6 susceptibility locus to the 5' regulatory promoter region shared by both the Parkinson's disease gene PARK2 and its co-regulated gene PACRG. According to The Leprosy Mission Canada, most people-–about 95% of the population-–are naturally immune to the disease.

Treatment

MDT anti-leprosy drugs: standard regimens

The WHO Study Group's report on the Chemotherapy of Leprosy in 1993 recommended two types of standard MDT regimen be adopted.The first was a 24-month treatment for multibacillary (MB or lepromatous) cases using rifampicin, clofazimine, and dapsone. The second was a six-month treatment for paucibacillary (PB or tuberculoid) cases, using rifampicin and dapsone. At the First International Conference on the Elimination of Leprosy as a Public Health Problem, held in Hanoi the next year, the global strategy was endorsed and funds provided to WHO for the procurement and supply of MDT to all endemic countries.

Between 1995 and 1999, WHO, with the aid of the Nippon Foundation (Chairman Yōhei Sasakawa, World Health Organization Goodwill Ambassador for Leprosy Elimination), supplied all endemic countries with free MDT in blister packs, channelled through Ministries of Health. This free provision was extended in 2000 with a donation by the MDT manufacturer Novartis, which will run until at least the end of 2010. At the national level, non-government organizations (NGOs) affiliated to the national programme will continue to be provided with an appropriate free supply of this WHO supplied MDT by the government.

MDT remains highly effective, and patients are no longer infectious after the first monthly dose. It is safe and easy to use under field conditions due to its presentation in calendar blister packs. Relapse rates remain low, and there is no known resistance to the combined drugs. The Seventh WHO Expert Committee on Leprosy, reporting in 1997, concluded that the MB duration of treatment—then standing at 24 months—could safely be shortened to 12 months "without significantly compromising its efficacy.