LEPROSY
The disease and its treatment
Microbiology
Leprosy is a chronic infectious disease caused by Mycobacterium leprae, an
acid-fast, rod-shaped bacillus. The disease mainly affects the skin, the
peripheral nerves, mucosa of the upper respiratory tract and also the eyes,
apart from some other structures. Leprosy has afflicted humanity since time
immemorial. It once affected every continent and it has left behind a
terrifying image in history and human memory - of mutilation, rejection and
exclusion from society.
Leprosy has struck fear into human beings for thousands of years, and was
well recognized in the oldest civilizations of China, Egypt and India. A
cumulative total of the number of individuals who, over the millennia, have
suffered its chronic course of incurable disfigurement and physical
disabilities can never be calculated.
Since ancient times, leprosy has been regarded by the community as a
contagious, mutilating and incurable disease. There are many countries in Asia,
Africa and Latin America with a significant number of leprosy cases. As of 1995
around 2 400 000 000 people live in countries where the prevalence of leprosy
is more than one case per 10 000 population. It is estimated that in 1995 there
are between one and two million people visibly and irreversibly disabled due to
past and present leprosy who require to be cared for by the community in which
they live.
When M.leprae was discovered by G.A. Hansen in 1873, it was the first
bacterium to be identified as causing disease in man. However, treatment for
leprosy only appeared in the late 1940s with the introduction of dapsone, and
its derivatives. Leprosy bacilli resistant to dapsone gradually appeared and
became widespread.
In 1995, there were an estimated 2 million cases in the world, most of them
concentrated in South-East Asia, Africa and the Americas. Among them 1.3
million are registered for treatment of whom 1 million are treated with Multi
Drug Therapy (MDT). The number of new cases detected worldwide each year is
about half a million.
Diagnosis of leprosy
Diagnosis of leprosy is most commonly based on the clinical signs and
symptoms.
These are easy to observe and elicit by any health worker after a short
period of training. In practice, most often persons with such complaints report
on their own to the health centre. Only in rare instances is there a need to
use laboratory and other investigations to confirm a diagnosis of leprosy.
In an endemic country or area, an individual should be regarded as having
leprosy if he or she shows ONE of the following cardinal signs:
- skin lesion consistent with leprosy and with definite sensory loss, with or
without thickened nerves
- positive skin smears
The skin lesion can be single or multiple, usually less pigmented than the
surrounding normal skin. Sometimes the lesion is reddish or copper-coloured. A
variety of skin lesions may be seen but macules (flat), papules (raised), or
nodules are common. Sensory loss is a typical feature of leprosy. The skin
lesion may show loss of sensation to pin pick and/or light touch. Thickened
nerves, mainly peripheral nerve trunks constitute another feature of leprosy. A
thickened nerve is often accompanied by other signs as a result of damage to
the nerve. These may be loss of sensation in the skin and weakness of muscles
supplied by the affected nerve. In the absence of these signs, nerve thickening
by itself, without sensory loss and/or muscle weakness is often not a reliable
sign of leprosy.
Positive skin smears: In a small proportion of cases, rod-shaped,
red-stained leprosy bacilli, which are diagnostic of the disease, may be seen
in the smears taken from the affected skin when examined under a microscope
after appropriate staining.
A person presenting with skin lesions or with symptoms suggestive of nerve
damage, in whom the cardinal signs are absent or doubtful should be called a
`suspect case' in the absence of any immediately obvious alternate diagnosis .
Such individuals should be told the basic facts of leprosy and advised to
return to the centre if signs persist for more than six months or if at any
time worsening is noticed. Suspect cases may be also sent to referral clinics
with more facilities for diagnosis.
Classification of leprosy
Leprosy can be classified on the basis of clinical manifestations and skin
smear results. In the classification based on skin smears, patients showing
negative smears at all sites are grouped as paucibacillary leprosy (PB), while
those showing positive smears at any site are grouped as having multibacillary
leprosy (MB).
However, in practice, most programmes use clinical criteria for classifying
and deciding the appropriate treatment regimen for individual patients,
particularly in view of the non-availability or non-dependability of the
skin-smear services. The clinical system of classification for the purpose of
treatment includes the use of number of skin lesions and nerves involved as the
basis for grouping leprosy patients into multibacillary (MB) and paucibacillary
(PB) leprosy.
While classifying leprosy, it is particularly important to ensure that
patients with multibacillary disease are not treated with the regimen for the
paucibacillary form of the disease.
Treatment of leprosy: MDT
The drugs used in WHO-MDT are a combination of rifampicin, clofazimine and
dapsone for MB leprosy patients and rifampicin and dapsone for PB leprosy
patients. Among these rifampicin is the most important antileprosy drug and
therefore is included in the treatment of both types of leprosy.
Treatment of leprosy with only one antileprosy drug will always result in
development of drug resistance to that drug. Treatment with dapsone or any
other antileprosy drug used as monotherapy should be considered as unethical
practice.
Rifampicin: The drug is given once a month. No toxic effects have been
reported in the case of monthly administration. The urine may be coloured
slightly reddish for a few hours after its intake, this should be explained to
the patient while starting MDT.
Clofazimine: It is most active when administered daily. The drug is well
tolerated and virtually nontoxic in the dosage used for MDT. The drug causes
brownish black discoloration and dryness of skin. However, this disappears
within few months after stopping treatment. This should be explained to
patients starting MDT regimen for MB leprosy.
Dapsone: The drug is very safe in the dosage used in MDT and side effects
are rare. The main side effect is allergic reaction, causing itchy skin rashes
and exfoliative dermatitis. Patients known to be allergic to any of the sulpha
drugs should not be given dapsone.
WHO-recommended MDT regimens
Multibacillary leprosy
For adults the standard regimens is:
Rifampicin: 600 mg once a month
Dapsone: 100 mg daily
Clofazimine: 300 mg once a month and 50 mg daily
duration: 24 months
Paucibacillary leprosy
For adults the standard regimens is:
Rifampicin: 600 mg once a month
Dapsone: 100 mg daily
duration: six months
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