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. This target has proved unattainable, to date. In 2011, the number of new cases diagnosed was 219,075 (excluding the small number of cases in Europe). These are concentrated in specific countries, often clustered in geographical sites and ethnic groups .
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. 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 . Infectivity appears to be low and many who become infected never manifest the disease . 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 . 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 .
The 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 . 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 . 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.
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 . In the male, damage to the testes can cause infertility, decreased testosterone and resultant bone thinning, impotence and male breast development .
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 . 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 
Diagnostics and Classification
Leprosy diagnostics involve a combination of clinical testing and identification of mycobacteria on skin test. This allows for the patient to be placed on the Ridley Jopling classification scale and guide management. Sensory nerve dysfunction can be measured using specialised filaments or by simple sensory discrimination using a ballpoint pen or cotton wool. Motor function can be assessed using voluntary muscle tests and, if available dynamometry,. Nerve conduction studies are the (often unavailable) gold standard.
In 1998 the WHO introduced  the simplified pauci- and multibacillary criteria to guide treatment. This field tool uses the number of skin lesions to dictate classification with paucibacillary type presenting up to 5 lesions and multibacillary type presenting 6 or more. Studies have shown that the addition of further information such as nerve testing can add to sensitivity and specificity of this simplified classification[15-16].
MDT (Multi-drug therapy) is highly effective (relapse of less than 1%) and prevents the emergence of resistant strains.
Paucibacillary disease is treated with a 6 month course of Rifampicin and Dapsone. Multibacillary disease is treated with Rifampicin, Clofazimine and Dapsone for a year.
Reactions and neuritis are treated with various regimes of steroids and steroid sparing alternatives. Neuritis can also be treated by surgical decompression although this remains unreliable as a technique to limit nerve damage.
Leprosy prevention would be the ideal approach to prevent related disability. Many programmes aim to limit transmission through MDT. New research into BCG vaccine (normally used to prevent TB) given in infancy and Rifampicin (an antibiotic) given to household contacts suggest a combined protective effect of about 80%  and if this strategy could be deployed it might prove the final step in control of the disease and prevent resulting disabilities.
Leprosy and Disability
Disabilities secondary to leprosy are variable and depend on a number of factors, including: the interplay between leprosy type, occurrence and duration of, the interval between infection and treatment. Nerve involvement can affect the eyes, the upper and lower limbs but early management can prevent lasting damage [18-19]. Management of established damage is more difficult and is largely a matter of reconstructive surgery to restore lost function using residual structures.
Measurement of Disability in the Leprosy Patient.
Disability can be comprehensively measured by the WHO’s International Classification of Functioning Disability and Health (ICF) which assesses all aspects of disability affecting quality of life . This holistic but complex scoring system is appropriate for any cause of disability but is not easily used in field settings. The WHO disability grading for leprosy is specific for the disease and is probably the most widely used scoring system. It involves scoring eyes, hands and feet on left and right.
The leprosy affected hand; impairment of normal function.
The function of the hand depends on many factors and especially on grip and sensation. Leprosy produces severe hand dysfunction through damage to the ulnar, median and, less frequently, the radial nerves. Loss of ulnar and median function paralyses the small muscles of the hand. This leads to loss of balance and synchronous movement of the digits, exacerbated by the uncontrolled pull of the long forearm muscles.
There is hyperextension (pulling of the finger toward the back of the hand) at the knuckle joint and Flexion (curling up) of the rest of the finger. An attempt to open the hand to grasp an object is usually achieved, in the normal hand, by a synchronous extension of the finger joints. In the clawed hand the patient’s hand is unable to spread out in preparation for grasping, since the fingers remain flexed.
Synchronous closing is also impaired. Normal closing of the hand allows for maximum contact with an object and maximal grip. Functioning small hand muscles ensure simultaneous and synchronised closing of the fingers around an object, with an even spread of pressure on the digit. In the clawed hand, the object is grasped with pressure on small areas: the tips of the fingers and the palm level with the knuckles.
Spreading out of the fingers is also lost. This limits the versatility of the hand, since the hand cannot conform to an uneven object wider than the palm. Advantageous grip is lost and effective grip strength is further diminished.
The thumb occupies a unique role in the hand, in a position to interact with all of the long digits. The mechanism of loss outlined above, also affects the thumb, with crucial loss of unique arcs of movement. Loss of closing of the thumb web space weakens or abolishes key grip , and the patient is unable to grasp an object between thumb tip and index finger. The unique ability for the human thumb to come across the palm to meet the other fingers is essential for the production of power grip to which the thumb contributes an estimated 40%. This movement also permits the grasping of a fine object between thumb, index and middle fingers (‘Chuck’ or ‘Three point’ grip) and very precise manipulative function can be achieved (e.g. holding a pen in writing).
This movement of the thumb is lost with paralysis of the median nerve, while pinch power will be maintained if the ulnar nerve is not affected; in most cases median and ulnar palsy occur together.
For around 60 years and especially since the pioneering work of Paul Brand, tendon and muscle unit transfer has been used to correct both these deformities , often in the same procedure. Many other ancillary procedures can be performed, to stabilize joints, to relieve contractures, to realign digits, all intended to make maximal use of residual muscle and tendon function.
The adequate range of joints and powerful, synchronous function of muscles is significantly handicapped by the loss of the other great modality in the hand – Sensation. Erik Moberg, who pioneered sensory testing in the hand, wrote ‘The insensate hand is the blind hand’.
Unlike the pure motor deficiency of the Polio afflicted hand, the leprosy hand loses both power and sensation. The available motor function is made inaccurate by the loss of joint position sense. Loss of protective sensation also makes the hands and feet vulnerable to secondary injury, ulceration and repeated infection. This leads to loss of length of the fingers (due to collapse and infection of bone), secondary scarring and contracture of the skin and tissues. Progressively, the almost useless leprosy mitten hand with no functioning fingers or thumb develops, leaving the patient severely disabled .
One must also bear in mind the added debilitation of these patients in societies and countries where Welfare and State safety net support is unavailable, or unreliable. These disabilities would be severely incapacitating, even in highly developed countries with adequate support provision.
Surgery in the leprosy patient has many roles. The surgeon can be involved in acute or chronic nerve management, in the management of ulcers and in reconstructive and cosmetic surgery.
Surgery in the leprosy hand aims to make maximal use of the available resources (still-functioning muscle units). Active tendons are transferred to more essential functions; contractures are released; joints are stabilised. The function overall is improved. All such surgery is directed at the motor aspects of the disability. No standard procedures are available for the restoration of sensation.
Principles of surgery in leprosy-affected hands include:
• Stiffness and limitation of movement at joints are corrected first.
• Instability of joints is corrected by procedures such as joint fusion or tenodesis (limitation of arc of movement).
• Dynamic instability, such as the claw hand, requires dynamic solutions, usually by the transfer of functioning muscle and tendon.
• Tendon transfer and stabilisation surgery should only be contemplated in the multi-drug therapy treated patient with a stable disability.
The timing of surgical corrections is also important. Surgery should not be attempted on an evolving picture, whether this is deteriorating or improving. It is generally accepted that tendon transfer surgery should not be considered before 6 months from established cure (non-infectivity) 
The improvement of function in the leprosy-affected hand with the use of tendon muscle unit transfer is dependent on several factors. A functioning tendon muscle unit must be available and in the case where multiple nerve palsies exist in a single limb these options can be limited. The power ratio and the excursion of the transferred muscle must match the function which is being restored .
Correction of the claw hand is based on the principle that if the knuckle joints can be stabilised at 5-10 flexion, muscles that open out the fingers will be able to open the hand for useful grip. The essential element is the reversal of the hyperextension deformity at the MCP joints (knuckles).
Median nerve paralysis produces atrophy of the thumb muscles. The thumb is habitually held flat in the plane of the palm (the ‘simian’ thumb) and movement across the palm to dialogue with the other fingers is lost. Opponensplasty restores the arc of movement of the thumb across the palm, such that its pulp apposes to the pulp of the long digits.
Opponensplasty aims to recreate the three-finger pinch and a grip of adequate strength. Almost every available tendon around the wrist has been used, and most of the procedures require the use of a pulley (around an existing structure) to change direction.
Surgical correction of radial nerve palsies is much less commonly indicated and is usually performed in combination with median and ulnar nerve paralysis. Triple nerve palsies occur in less than 1% of those with nerve involvement due to leprosy[25-26].
The use of surgery in the management of ulcer care, correction of nerve palsies in the lower limb, eye care and aesthetic facial surgery are also part of the surgical repertoire for leprosy patients.
© Nola Lloyd 2011
Modified from Dr Nola Lloyd’s Dissertation for MSc Tropical Medicine and International Health,
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