Leprosy, also known as Hansen's disease, is a chronic disease caused by a mycobacterium and virtually restricted to tropical zones. Leprosy leads to skin nodules with loss of pigmentation, mucous membrane lesions in nose and pharynx, and neuritis with nerve thickening, loss of pain sensation, and patchy weakness, often involving ace and intrinsic hand muscles. Diagnosis is by demonstrating the organisms in stained scrapings or by skin or nerve biopsy. The type of disease caused depends on the number of bacteria encountered and basic resistance to the disease.


Cause of leprosy

Leprosy is caused by a bacillus (rod-shaped) bacterium known as Mycobacterium leprae (see mycobacterial diseases). M. leprae was discovered by G. A. Hansen in Norway in 1873, is a slow growing, intracellular pathogen, incapable of living outside its host. The organism has never been grown in a laboratory, making it more difficult to study than other bacteria; at this point it can only be grown in animals. Armadillos and immunocompromised mice are the only two sources for growing the bacteria for research purposes.


Another factor complicating studies of leprosy is that M. leprae multiplies slowly, with an average doubling time of 12–14 days, and only in a select group of animals. Armadillos and three species of monkeys – chimpanzees, sooty mangabeys, and cynomolgous macaques – are the only animals other than humans that have been found to become naturally infected with M. leprae. Symptoms can take as long as 20 years to appear.


The mode of transmission of leprosy is still unclear and has been assumed to be via the respiratory system mainly through nasal droplets; broken skin also remains a possibility. The primary tissues that are affected by M. leprae are the superficial sites of the skin and peripheral nerves because the bacteria survive best at low temperatures.


Leprosy has been described by Ridley and Joplin as a continuous spectrum of disease. The course of human leprosy depends on the immunity of infected persons. Some people in a family may have the infection, but other close family members will not develop it, depending on their personal ability to fight off the bacteria.


Leprosy usually affects the skin, peripheral nerves and upper airways but has a wide range of clinical manifestations. Clinical forms of leprosy represent a spectrum reflecting the cellular immune response to M. leprae. Patients with good T-cell immunity (Th1 type) exhibit tuberculoid (TT) leprosy which is also known as pauci-bacillary leprosy, a milder form of the disease, characterized by skin discoloration. Those with poor T-cell immunity typically exhibit lepromatous (LL) leprosy or multi-bacillary leprosy which is associated with symmetric skin lesions, nodules, plaques, thickened dermis, and frequent involvement of the nasal mucosa resulting in congestion and nose bleeds. In between these forms of leprosy are the borderline tuberculoid (BT), borderline-borderline (BB) and borderline lepromatous (BL) forms.


LL leprosy is also characterized by large numbers of organisms in the skin, many skin lesions with slight hypopigmentation, and less sensory loss in the lesions. While individuals with LL have high titer antibodies to M. leprae, they also have an impaired cellular immune response to the bacillus. Changes in immunity of the host as well as treatment can result in worsening of the clinical course of the disease.


All forms of leprosy may cause some degree of peripheral neurological damage (nerve damage in the arms and legs) which causes sensory loss in the skin as well as muscle weakness. People with long-term leprosy may lose the use of their hands or feet due to repeated traumatic injury resulting from lack of sensation. If left untreated, it can cause progressive and permanent damage to the skin, nerves, eyes and limbs.


Diagnosis and treatment

In the United States, most physicians do not have experience identifying leprosy because it is extremely rare (about 100–200 new cases per year, mostly occurring in the Gulf Coast, Hawaii, Massachusetts, and New York and among individuals who have lived in areas of the world where the disease is more widespread). It is important that people who have unusual rashes that do not respond to treatment seek out skilled dermatologists who can make an accurate diagnosis.


Diagnosis of leprosy is typically based on clinical symptoms, especially localized skin lesions that show sensory loss (loss of sensation to stimuli such as touch and heat). Thickened, enlarged peripheral nerves are also a hallmark of the disease. Skin and blood samples can also be tested in order to reach a conclusive diagnosis.


With early diagnosis, leprosy can be treated. People who are getting treatment for leprosy are not contagious, and they can lead a normal lifestyle.


In 1981, the World Health Organization (WHO) recommended multidrug therapy (MDT) with dapsone, rifampicin, and clofazimine. The regimen for multibacillary is monthly for a period of one year and for paucibacillary it is monthly doses of rifampicin and daily doses of dapsone for a period of six months. Although several groups are now advocating uniform treatment for all forms of leprosy; this is being debated in the scientific community.


Leprosy today

At the beginning of 2007, the registered prevalence of leprosy in the world was 224,717 cases, while the number of new cases detected during 2006 was 259,017, as reported by 109 countries (World Health Organization). The global number of new cases detected during the past five years has decreased at an average rate of nearly 20% per year largely due to the success of early diagnosis and treatment with MDT.


Since the 1980s, when the World Health Organization (WHO) initiated its Leprosy Elimination Project, more than 14 million cases have been cured. However, the number of new cases being detected annually is raising the unanswered questions about the source of infection, transmission, and incubation period of leprosy. In other words, what is the basis of this steady stream of new cases detected in the midst of such a dramatic drop in the numbers of people living with the disease? This may be attributed to a number of factors including intensified efforts in case detection, and/or high transmission of the disease in certain areas.


Today, leprosy is found mainly in Angola, Brazil, Central African Republic, Democratic Republic of Congo, India, Madagascar, Mozambique, Nepal, and the United Republic of Tanzania. These countries account for a remarkable 75% of the global leprosy burden and they are taking steps to control the disease through information campaigns and by providing diagnostic and treatment services to all communities, including the poor and underserved, and by incorporating leprosy diagnosis and treatment into general health services.


History of the disease

Leprosy was well recognized in the oldest civilizations of China, Egypt and India. The first known written reference to leprosy appeared in an Egyptian papyrus document written around 1550 BC.


Throughout history, leprosy has been feared and misunderstood, and has resulted in significant stigma and isolation of those who are afflicted. It was thought to be a hereditary disease, a curse, or punishment from the gods. During the Middle Ages, those with leprosy were forced to wear special clothing and ring bells to warn others as they walked by.


A cumulative total of the number of individuals who, over the millennia, have suffered its chronic course of incurable disfigurement, physical disabilities or psychological trauma can never be estimated. There are many countries in Asia, Africa and Latin America with a significant number of leprosy cases and between one to two million people are visibly and irreversibly disabled due to past and present leprosy.


In 1921, US Public Health Service established the nation's first leprosarium, located in what is now known as Carville, Louisiana. The leprosarium served as an institution for persons with leprosy, a hospital for experiments with treatments for leprosy as well as a laboratory to study the organism. The center, which became known simply as "Carville," became a refuge for leprosy patients and one of the premier centers of scientific research and testing in attempts to find a cure for Hansen's Disease.


In 1941, the discovery of Promin, a sulfone drug, was shown to successfully cure leprosy, but this treatment also involved painful injections. Promin became known as the "Miracle of Carville." In the 1950s Dapsone pills, pioneered by R. G. Cochrane at Carville, became the treatment of choice for leprosy. Dapsone worked wonderfully at first, but M. leprae eventually began developing dapsone resistance.


In the 1970s the first successful multi-drug treatment (MDT) regimen for leprosy was developed through drug trials on the island of Malta. In 1981, The World Health Organization began recommending MDT, a combination of three drugs: dapsone, rifampicin, and clofazimine. MDT takes from six months to a year or even more, depending on clinical manifestations of the leprosy infection.


In 1986, the Carville facility became known Gillis W. Long Hansen's Disease (Leprosy) Center, named after the distinguished United States Congressman, close friend and associate of the people working and living with leprosy. During its century of service, Carville was home to several hundreds of patients, some of whom met and married there and spent a majority of their lives on the picturesque campus. When Carville closed in 1998, its few remaining patients were reluctant to leave.