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Leprosy, a disease caused by Mycobacterium leprae, is fully curable if diagnosed and treated early, before permanent neurological damage sets in. The neuropathy that occurs in leprosy is the reason for the disfigurement and disability associated with the disease, but it is neither inevitable nor untreatable.
In other words, the complications of leprosy are not due to the effects of the mycobacteria themselves, but rather due to the nerve compression that is secondary to the immune reaction of the host.
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Leprosy reactions occur during, before, or after treatment of leprosy. They exacerbate the neuropathy unless promptly treated, but are immunological in origin. They are of two types - type 1 or reversal reactions, and type 2 or erythema nodosum leprosum.
Leprosy reactions must be treated in a timely and effective manner to prevent nerve compression and resulting sensory loss, which inevitably leads to mutilating deformity. The reactions involve increased pain, inflammation, and infiltration. All of these should be managed to prevent nerve damage.
Typical changes in leprosy reactions include the emergence of new skin lesions, or existing lesions becoming red and swollen, and more tender. Tender cutaneous nodules may also appear. Neurological complications occur in the form of inflammation of peripheral nerves, causing swelling, tenderness, frequent loss of function such as anesthesia or weakness of the muscles supplied by the involved nerve. Thus hand or foot weakness, or inability to fully close the eyes, may occur suddenly as a result of leprosy reactions.
Prompt diagnosis and treatment usually reduce the severity of the reactions and their sequelae. Drugs used to manage these reactions include:
Corticosteroids are usually preferred, and multi-drug treatment (MDT) should always be continued. Non-steroidal anti-inflammatory drugs (NSAIDs) are used in mild reactions. Steroids should be tapered over 12-20 weeks to avoid rebound inflammation. Clofazimine is a more long-term agent.
Cyclosporine or methotrexate are immunosuppressants, which may be used in place of corticosteroids to treat leprosy reactions when there is steroid allergy or when severe adverse effects develop with corticosteroid therapy.
In leprosy, the peripheral nerve trunks are invaded by the bacilli and inflammatory cells. This will cause neuritis, the features of which include tenderness, thickening, and irregularity of the nerve, as well as sensorimotor involvement. This usually comes on in a subacute manner, and the changes may be silent in some cases.
The nerve changes lie at the root of the typical deformities characteristic of leprosy. In most patients, a mixed or sensorimotor neuropathy occurs. This involves a single nerve. As a result of skin denervation, the associated glands and hair follicles die, which results in skin dryness, fissuring, and ulceration. Neuropathic pain may also occur.
The breaching of the integument gives rise to secondary infection of underlying bone and soft tissue. Finally the bone is resorbed at the site of infection, giving rise to deformity. The bone involvement may also lead to gross deformation of the nose skeleton and ensuing creation of a saddle-nose deformity.
The nerves commonly involved include the facial, trigeminal, ulnar, median, and radian nerves, as well as the common fibular and posterior tibial nerves. Involvement of the facial nerve leads to failure of eyelid closure and lagophthalmos. The nasal mucosa becomes dry and hypoesthetic, as does the cornea and conjunctiva.
Leprosy can cause eye damage both through the involvement of the branches of the facial nerve innervating the eye or by direct infection of the skin or the eye. Either of these leads to:
These normally culminate in blindness which occurs in over three percent of patients, and may prove to be cut off a valuable route of information following anesthesia of the hands and feet.
Ulnar or median nerve involvement leads to hypoesthesia or anesthesia of the hand, as well as paralysis of the intrinsic muscles of the hand. This results in claw hand deformity, produced by hyperextended metacarpophalangeal joints and flexed interphalangeal joints.
Skin denervation leads to anhidrosis and poor autonomic function, as a result of which ulceration and secondary infection occurs. This progressively erodes the fingers and leaves only stumps behind. The flexors of the fingers and wrist may also be paralyzed, while the loss of thumb opposition also occurs.
When the ulnar and median nerves are involved at higher levels, there is impaired flexor and extensor action of the forearm muscles, producing ulnar deviation at the wrist. This loss of flexor function makes it hard to hold objects, or handle smaller objects.
Radial nerve involvement is rare, and in fact occurs only as part of triple paralysis (ulnar, median, and radial paralysis). It causes drop wrist due to extensor paralysis, which makes it difficult to hold objects.
Neuropathy of the lower limbs frequently happens. When the common fibular nerve or either of its branches is involved, it results in hypoesthesia or anesthesia of the corresponding area of the lower limb. The ankle and toe dorsiflexors may be affected depending on the nerve damage. When both branches are affected, it leads to foot drop.
Moreover, muscle atrophy leads to shrinking of the anterior and lateral parts of the leg. If the posterior tibial nerve is damaged, the sole becomes anesthetic, the intrinsic muscles of the foot are paralyzed, and clawing of the toes develops. Ulceration and loss of toes are almost inevitable.
Systemic involvement may occur in patients with multibacillary leprosy as a result of leprosy reactions, or less commonly because of infection by the bacteria in the blood stream. Renal damage may occur due to type 2 reactions or by secondary amyloidosis affecting many organs.
This is most commonly observed when leprosy takes a chronic course with many reactions occurring and being treated. Renal affection may manifest as glomerulonephritis, interstitial nephritis, or other renal conditions. As a result, renal failure may ensue.
Pulmonary tuberculosis is often seen. The upper airway is affected in many cases. Generalized abnormalities of the peripheral vessels and endothelial cell infection are common, with ischemic ulceration and autonomic dysfunction of the cardiovascular system. Peripheral arteries may show abnormalities.
Orchitis is common (90 percent), with the potential for infertility and impotence. A third of patients may have adrenocortical lesions with iatrogenic adrenocortical failure. Hepatic amyloidosis may occur, while pancytopenia due to infiltration of bone marrow, bacteremia, and lymphadenopathy are often seen.
While leprosy reactions are unpredictable, the resulting disability is preventable and reversible if caught in time. It is important to train patients on self-care as the primary means to prevent disability, which includes teaching them to:
Health care providers should follow the following procedures as well:
Community intervention in leprosy is essential to spread the awareness of the early signs of the disease and to motivate people to come in for early diagnosis. This alone can ensure that early intervention takes place, helping in turn to avoid or mitigate serious or disfiguring complications as a consequence of neuropathy, as well as its secondary consequences such as ulceration and secondary infection. In turn, physical deformity will be avoided, preventing any future stigma of leprosy.