The awareness of the Japanese public regarding Hansen's disease has been enhanced by the judgment on May 11, 2001 regarding the suit demanding compensation for the Hansen's disease to the Japanese Government filed at the Kumamoto district court, the subsequent statements delivered by the government, the comments made by the Prime Minister, etc. However the current situation regarding the diagnosis and treatment of Hansen's disease remains virtually unknown.
1. What is Hansen's disease?
     Hansen's disease is a chronic infectious disease caused by the acid-fast bacillus Mycobacterium leprae(M.leprae) 1). Though its culture has been so far impossible, advances should be achieved in fundamental research since all the genes have been identified. The major lesions are localized under the skin and in the peripheral nerves, and the bacterium seldom penetrates the internal organs. The source of infection is untreated patients in whom a high number of M. leprae is evidenced. The disease is reportedly spread through respiratory droplets. The time of infection poses practically no problem except in case of severe infection during infancy when the immune system does not function sufficiently. Besides the time between the infection and disease onset is long (several years~10 years~ several decades), since various factors such as the immunocompetence of the body, the number of bacteria, the environment, etc. are involved.
     The annual number of new patients in Japan has recently been six or so native residents and about eight foreign residents (Figure) 2). The decrease in the number of Japanese new patients has been remarkable, and most of them are individuals in the 60-plus age bracket. On the other hand, many foreigners residing in Japan who contract this disease are young workers from Brazil, the Philippines and other countries.
2. Present situation of outpatient diagnosis and treatment
     Hansen's disease can now be diagnosed and treated under health insurance coverage following the abolishment of the "Leprosy Prevention Act". Most of the new patients are diagnosed and treated in the dermatology departments of university hospitals or of general hospitals.
     The skin lesions at the initial stage of Hansen's disease show various forms such as erythema, papules, annular spots, etc. that do not itch. There are no skin lesions specific to Hansen's disease. Sensory dumbness (sensation of touch, pain and temperature) and paralysis as well are commonly evidenced with the skin lesions. Hyperplasia of the peripheral nerves and dyskinesia are also observed.
     During medical examination, the differentiation of Hansen's disease is based upon the place of birth of the subject, childhood history, skin lesions without subjective symptoms, sensory anomalies, nerve hyperplasia, etc., and detection of M.leprae (skin smear test, histopathological staining, PCR test, etc.) and skin pathological tests are performed.
3. Tests required for Hansen's disease
a) Skin smear test: since a large number of M. leprae is present under the skin, skin tissue fluid is collected with the aid of      a scalpel. It is smeared on a slide glass, followed by acid-fast staining and microscopic examination.
b) Neurological tests: the sensation of touch, of pain and of temperature is tested. Nerve hyperplasia, dyskinesia, etc. are also                checked.
c) Histopathological tests: granulomas, invasive cells, etc. are observed. M. leprae is evidenced by means of acid-fast           staining.
d) PCR test: this is a test for identifying Mycobacterium leprae specific DNA. The specimens used are skin tissues, blood, etc.
4. Diagnosis of Hansen's disease
     The diagnostic process differs between Japan and the WHO. In Japan, since a substantial amount of time is spent to observe the patients and a whole battery of tests is performed, the diagnosis is made by integrating four parameters, namely skin lesions (with no subjective symptoms), nerve symptoms (sensory anomalies, hyperplasia, dyskinesia), detection of Mycobacterium leprae and histopathological tests (Table 1). In contrast, in developing countries where the WHO plays a leading role, since there are more health care workers than physicians in the front line of diagnosis and treatment of Hansen's disease, this ailment is oftentimes diagnosed on the basis of skin lesions followed by perception dumbness (Table 1).
     Diversity is observed amid patients in terms of number of M. leprae, nature and number of skin lesions, sensory disorders, nerve hyperplasia, dyskinesia, histopathological findings, etc. However these are differences in the immune status of the body to M. leprae, and they are classified as disease forms (Table 2). They are classed as group I of the initial stage of onset, followed by type TT with a high immunocompetence toward M. leprae, type LL with no reaction at all, B group in-between these types (BT type, BB type, BL type) (Ridley-Jopling classification). Besides the TT type is also classified as paucibacillary type (PB), since it is difficult to detect M. leprae in tests, and the LL type is also classed as multibacillary type (MB), since M. leprae can be detected. This classification into PB and MB is also applied when selecting the therapy.
5.Treatment
     The treatment is in principle the multi-drug treatment recommended by the WHO using Hansen's disease treatment agents (rifampicin, DDS (sulfa drug), clofazimine (pigment-based antimicrobial). These drugs are taken orally from six months (paucibacillary type) to one year (multibacillary type). In Japan, the duration of the treatment may be lengthened, and therapy associating a fluoroquinone agent is also used.
     When treating Hansen's disease it is paramount not to leave sequels such as neuropathy, etc. Therefore the attention should be paid to initiate early the diagnosis and treatment. Hansen's disease can be cured, but regular ambulatory follow-up is also important after treatment to prevent relapse of skin lesions, leprosy reactions and nerve damage.
Conclusion
     Hansen's disease is an ordinary bacterial infectious disease, and its infectivity is extremely low. Moreover onset is rare. It is necessary to make a diagnosis at the early stage and not to leave nerve damage. The diagnosis is made by integrating four parameters, namely skin lesions during decrease in perception, neuroparalysis-hyperplasia-dyskinesia, detection of M. leprae, and histopathological findings. The treatment is carried out in compliance with the WHO' guidelines on treatment.
     On the other hand, it is still necessary to exercise prudence during diagnosis and treatment in general health care institutions, due to the prejudices and discrimination that have been prevailing from a long time ago. It is important to fully understand the meaning of the abolishment of the "Leprosy Prevention Act" in 1996 and the comments made by the Prime Minister on the judgment of the court regarding the suit demanding compensation to the Government for the Hansen's disease in May 2001. It is also paramount to do efforts to provide education on this disease.
Reference literature
1. Sasaki S, Takeshita F, Okuda K, Ishii N: M. leprae and leprosy: a compendium. Microbiol Immunol 45: 729-736,           2001.
2. 2. Ishii N, Onoda M, Sugita Y, et al. Survey of newly diagnosed leprosy patients in native and foreign residents of Japan.                     International.J.Lepr. 2000: 68: 172-176.
Table 1 - Diagnosis of Hansen's disease
Diagnosis in Japan
Diagnosis made by integrating the following four parameters
a) Skin lesions followed by decrease in perception
b) Neuroparalysis, hyperplasia, dyskinesia
c) Detection of M. leprae
d) Histopathological findings
WHO's diagnosis
Compliance with at least one of the three following parameters
a) Skin lesions followed by loss of perception
b) Hyperplasia of the peripheral nerves followed by loss of perception
c) Positiveness to the skin smear test