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Click on images to enlarge Perspectives/Leprosy: Facts
Leprosy and Reconstructive Hand Surgery [1].
Leprosy disease burden and initiatives for control.
Despite decades of intensive effort to control leprosy the disease remains an important global issue. In 1985 it was estimated that approximately 12 million people worldwide were affected by leprosy. The eradication of leprosy by the new millennium was first proposed in the 1980’s. This laudable aim was later modified to “elimination as a public health problem” and adopted by the World Health Assembly[5]. This target has proved unattainable, to date. In 2006, prevalence was registered at just under two hundred and twenty five thousand [2]. These are concentrated in specific countries, often clustered in geographical sites and ethnic groups [3].
The study of leprosy is complex, partly, and largely, due to the lengthy disease progression and the predilection for the poorest, most marginalised communities. Initiatives aimed at early diagnosis and the availability of free multi-drug therapy through the World Health Organisation (WHO) have led to the decline of leprosy infection. Misconceptions and misdirection about global policy have also affected the picture of leprosy in the world today. Eradication (total absence) and elimination (less than 1 case per 10,000 population) are terms often, and mistakenly, used interchangeably. The natural desire for countries to achieve the goals set by the WHO have led to misreporting and rendered reports of disease monitoring unreliable. The WHO’s targets have proved unattainable, to date, in various countries. Areas where leprosy remains a problem and the WHO’s target is still elusive include India, Nepal, Angola, Brazil, Central African Republic, Democratic Republic of Congo, Mozambique, Tanzania and Madagascar[2]. The single largest concentration is in India.
Data on elimination and monitoring of disease and of infection rates, does not take account of the permanent damage left by the infection. Paralysis of nerves and the stigmata of leprosy infection (paralysed clawed hands, leonine facies, collapsed nasal bridge, absent eyebrows, deformation of fingers and toes) remain as permanent features after the patient has been cured of infection. These patients, who, for the purposes of achieving ‘cure’ targets are considered cured, are nevertheless severely incapacitated and form part of an unclassified and relatively unmonitored demographic.
Leprosy the Cause and Transmission
Leprosy is a disease caused by Mycobacterium Leprae. The mycobacterium has a predilection for, and colonises, nerve cells causing a chronic granulating infection of nerves and skin [7]. Infectivity appears to be low and many who become infected never manifest the disease [8]. Leprosy is difficult to contract and once treated is no longer infectious. In the spread of the disease, longstanding, close proximity does appear to be the most important factor. An individual living with a untreated leprosy affected person runs 2-10x increased risk of contracting the disease depending on the leprosy type [9]. It is thought that infection is due to nasal secretions and airway spread. Man is the only known disease reservoir although Mycobacterium Leprae has been shown to survive in the nine-banded armadillo.
M. Leprae is difficult to study due to the slow evolution of the disease, the lack of animal models and our inability to grow the organism in culture. Disease presentation is largely dictated by an individual’s immune response. This separates those with Tuberculoid Leprosy (a strong immune response to a small mycobacterial burden), from Lepromatous leprosy (patients with minimal inflammatory response to a heavy mycobacterial load). Between these extremes are borderline types. Intervals between infection and disease presentation are variable; on average,10 years for lepromatous leprosy and about half that time for tuberculoid leprosy [9].
T
he two extremes of disease are generally stable. Those suffering from borderline types are prone to flare ups known as reactions. Reactions are of two possible types: Type 1, which can affect all types of borderline leprosy and also postpartum women, and is due to delayed hypersensitivity to M. Leprae in nerves and skin [10]. ENL (Erythema Nodosum Leprosum) or type 2 reactions affect those with lepromatous or borderline lepromatous leprosy. This is due to specific immune cell dysfunction secondary to the leprosy with excessive inflammation and immune complex deposition in skin nerves and organs [10]. Nerve inflammation can also occur separate to reactions and can be acute, chronic or silent (with no symptoms until the appearance of a new disability). Nerve involvement can leave patients with combinations of numbness and paralysis leading to progressive disability and stigmatising disfigurement. Reactions and neuritis can occur before, during and even after successful treatment of leprosy with drugs.
Clinical manifestations and complications
Leprosy is a complex disease with a host of slow and fast evolving presentations. The cardinal symptoms and signs of leprosy are;
• Discoloured numb skin lesions.
• Thickened peripheral nerves.
• Presence of the leprosy bacillus on specialised skin testing[10].
•
Skin lesions are often the first presentation. These are usually ill defined pale areas with none or mild sensory impairment. Other symptoms include non-pale areas of numbness or muscle weakness. Occasionally patients can present with reactions and systemic symptoms including fever and enlarged lymph nodes.
In established disease the spectrum of presentation reflects the complex interaction between the leprosy mycobacterium and the patient’s immune response.
In lepromatous disease skin lesions have ill-defined edges, are symmetrical and numerous. Nerve damage is slow to appear and usually presents on one side in the limbs. Sensation is commonly affected first with later development of weakness. There can be dense skin infiltration causing damage to the eyes, face (Leonine facies) and collapse of the nose Organ damage of insidious onset can also occur [9]. In the male, damage to the testes can cause infertility, decreased testosterone and resultant bone thinning, impotence and male breast development [9].
Tuberculoid leprosy occupies the other end of the spectrum, often with only one or a few skin lesions with discrete borders and red/orange coloration. Nerve damage is early and skin tests show low levels of the mycobacteria [11]. Lesions can self heal, leaving no impairment; however with larger inflamed lesions there is greater risk of local and more distant nerve involvement. Specific major peripheral nerves not directly involved with skin lesions are commonly affected.
• Ulnar nerve at the elbow.
• Posterior tibial nerve as it traverses behind the ankle.
• Common peroneal nerve behind the knee.
• Radial nerve at the wrist.
• Nerves to the face and eyes (often visible through thin skin).
• Median nerve at the wrist.
Sensory nerve function is usually affected first. Sensory, motor and autonomic impairment can occur synchronously. Despite the range of complications that occur in leprosy it is thought that many who are infected do not manifest the disease and of those who do, only 2% progress to long term disability [12]
