Leprosy, also known as Hansen’s disease, is a chronic, systemic infection characterized by progressive cutaneous lesions. It's caused by Mycobacterium leprae, an acid-fast bacillus that attacks cutaneous tissue and peripheral nerves, producing skin lesions, anesthesia, infection, and deformities.
With timely and correct treatment, leprosy has a good prognosis and is seldom fatal. Untreated, however, it can cause severe disability. The lepromatous type may lead to blindness and deformities.
Leprosy occurs in three distinct forms:
❑Lepromatous leprosy, the most serious type, causes damage to the upper respiratory tract, eyes, and testes as well as to the nerves and skin.
❑Tuberculoid leprosy affects peripheral nerves and sometimes the surrounding skin, especially the face, arms, legs, and buttocks.
❑Borderline (dimorphous) leprosy has characteristics of both lepromatous and tuberculoid leprosies. Skin lesions in this type of leprosy are diffuse and poorly defined.
Contrary to popular belief, leprosy isn’t highly contagious; it actually has a low rate of infectivity. Continuous, close contact is needed to transmit it. In fact, 9 out of 10 persons have a natural immunity to it. Susceptibility appears highest during childhood and seems to decrease with age. Presumably, transmission occurs through nasal droplets containing M. leprae or by inoculation through skin breaks (with a contaminated hypodermic or tattoo needle, for example). The incubation period is unusually long — 2 to 40 years with an average of 5 to 7 years.
Leprosy is most prevalent in the underdeveloped areas of Asia (especially India and China), Africa, South America, and the islands of the Caribbean and Pacific. About 6 million people worldwide suffer from this disease; approximately 7,000 are in the United States, mostly in California, Texas, Louisiana, Florida, New York, and Hawaii.
M. leprae attacks the peripheral nervous system, especially the ulnar, radial, facial, anterior-tibial, and posterior-popliteal nerves. The central nervous system appears highly resistant. When the bacilli damage the skin's fine nerves, they cause anesthesia, anhidrosis, and dryness. If they attack a large nerve trunk, motor nerve damage, weakness, and pain occur, followed by peripheral anesthesia, muscle paralysis, or atrophy. In later stages, clawhand, footdrop, and ocular complications — such as cor-neal insensitivity and ulceration, conjunctivitis, photophobia, and blindness — can occur. Injury, ulceration, infection, and disuse of the deformed parts cause scarring and contracture. Neurologic complications occur in both lepromatous and tuberculoid leprosy but are less extensive and develop more slowly in the lepromatous form. Lepromatous leprosy can invade tissue in virtually every organ of the body, but the organs generally remain functional.
The lepromatous and tuberculoid forms affect the skin in markedly different ways. In lepromatous disease, early lesions are multiple, symmetrical, and erythematous, sometimes appearing as macules or pap-ules with smooth surfaces. Later, they enlarge and form plaques or nodules called lepromas on the earlobes, nose, eyebrows, and forehead, giving the patient a characteristic leonine appearance. In advanced stages, M. leprae may infiltrate the entire skin surface. Lepromatous leprosy also causes loss of eyebrows, eyelashes, and sebaceous and sweat gland function and, in advanced stages, conjunctival and scleral nodules. Upper respiratory lesions cause epistaxis, ulceration of the uvula and tonsils, septal perforation, and nasal collapse. Lepromatous leprosy can lead to hepatosplenomegaly and orchitis. Fingertips and toes deteriorate as bone resorption follows trauma and infection in these insensitive areas.
When tuberculoid leprosy affects the skin (sometimes its effect is strictly neural), it produces raised, large, erythematous plaques or macules with clearly defined borders. As they grow, they become rough, hairless, and hypopigmented and leave anesthetic scars.
In borderline leprosy, skin lesions are numerous but smaller, less anesthetic, and less sharply defined than tuberculoid lesions. Untreated, borderline leprosy may deteriorate into lepromatous disease.
Occasionally, acute episodes intensify leprosy’s slowly progressing course. Whether such exacerbations are part of the disease process or a reaction to therapy remains controversial. Erythema nodosum leprosum (ENL), seen in lepromatous leprosy, produces fever, malaise, lymphadenopathy, and painful red skin nodules, usually during antimicrobial treatment, although it may occur in untreated people. In Mexico and other Central American countries, some patients with lepromatous disease develop Lucio's phenomenon. This malady produces generalized punched-out ulcers that may extend into muscle and fascia. Leprosy may also lead to secondary bacterial infection of skin ulcers and to amyloidosis.
Early clinical indications of skin lesions and muscular and neurologic deficits are usually sufficiently diagnostic in patients from endemic areas. Biopsies of skin lesions are also diagnostic. Peripheral nerve biopsy or smears of the skin or of ulcerated mucous membranes help confirm the diagnosis. Blood tests show increased erythrocyte sedimentation rate; decreased albumin, calcium, and cholesterol levels; and, possibly, anemia.
Treatment consists of antimicrobial therapy using sulfones, primarily oral dapsone, which may cause hypersensitivity reactions. Hepatitis and exfoliative dermatitis, although uncommon, are especially dangerous reactions. If they occur, sulfone therapy should be stopped immediately.
Failure to respond to sulfone or the occurrence of respiratory involvement or other complications requires the use of alternative therapy, such as rifampin in combination with clofazimine or ethionamide. Clawhand, wristdrop, or footdrop may require surgical correction.
When a patient's disease becomes inactive, as determined by the morphologic and bacterial index, treatment is discontinued according to the following schedule: tuberculoid, 3 years; borderline, depends on the severity of the disease but may be as long as 10 years; lepromatous, requires lifetime therapy.
Because ENL is commonly considered a sign that the patient is responding to treatment, antimicrobial therapy should be continued. Thalidomide and clofazimine have been used successfully to treat ENL at the National Hansen's Disease Center (NHDC); however, this treatment requires a signed consent form and strict adherence to established NHDC protocols. Corticosteroids may also be given as part of ENL therapy.
Any patient suspected of having leprosy may be referred to the Gillis W. Long Hansen's Disease Center in Carville, Louisiana, or to a regional center. At this international research and educational center, patients undergo diagnostic studies and treatment and are educated about their disease. Patients are encouraged to return home as soon as their medical condition permits. The federal government pays the full cost of their medical and nursing care.
Patient care is supportive and consists of measures to control acute infection, prevent complications, speed rehabilitation and recovery, and provide psychological support.
❑Give antipyretics, analgesics, and sedatives, as needed. Watch for and report ENL or Lucio's phenomenon.
❑Although leprosy isn’t highly contagious, take precautions against the possible spread of infection. Tell patients to cover coughs or sneezes with a paper tissue and to dispose of it properly. Take infection precautions when handling clothing or articles that have been in contact with open skin lesions.
❑Patients with borderline or lepromatous leprosy may suffer associated eye complications, such as iridocyclitis and glaucoma. Decreased corneal sensation and lacrimation may also occur, requiring patients to use a tear substitute daily and protect their eyes to prevent corneal irritation and ulceration.
❑Stress the importance of adequate nutrition and rest. Watch for fatigue, jaundice, and other signs of anemia and hepatitis.
❑Tell the patient to be careful not to injure an anesthetized leg by putting too much weight on it. Advise testing bath water carefully to prevent scalding. To prevent ulcerations, suggest the use of sturdy footwear and soaking feet in warm water after any kind of exercise, even a short walk. Advise rubbing the feet with petroleum jelly, oil, or lanolin.
❑For patients with deformities, an interdisciplinary rehabilitation program employing a physiotherapist and plastic surgeon may be necessary. Teach the patient and help him with prescribed therapies.
❑Provide emotional support throughout treatment. Communicating accurate information about leprosy to the general public, especially to health care professionals, is a function of primary importance for the entire staff at the NHDC.
Review other book chapters online related to Leprosy:
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Professional Guide to Diseases (Eighth Edition) Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2005 ISBN: 1-58255-370-X 
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