Leprosy is a chronic, progressive bacterial infection. It primarily affects the nerves of the extremities, the lining of the nose, and the upper respiratory tract. It is caused by the bacteria Mycobacterium leprae. Leprosy produces skin sores, nerve damage, and muscle weakness if left untreated. It can cause severe disfigurement and significant disability.
Leprosy is one of the oldest diseases in recorded history. According to the World Health Organization (WHO), the first known written reference to leprosy is from 600 B.C. (WHO, 2010).
Leprosy is common in many countries, especially those with tropical or subtropical climates. However, it is not as commonin the United States. The National Institutes of Health (NIH) reports that only about 100 new cases are diagnosed in the United States each year (NIH, 2011).
More than half of leprosy cases reported in the United Statesin 2006 were found in California, Florida, Louisiana, Massachusetts, New York, and Texas. The majority of cases involved people emigrating from developing countries(Merck, 2009).
There are three systems for classifying leprosy.The first system recognizes two types of leprosy—tuberculoid and lepromatous. These are based on a person’s immune response to the disease.
The immune response is good and the disease is limited to a few lesions (sores on the skin) in tuberculoid leprosy. The disease is mild and only slightly contagious. The immune response is poor in lepromatous leprosy and affects the skin, nerves, and other organs. Lesions andnodules (large lumps and bumps) are widespread. The disease is more contagious.
WHO categorizes the disease based on the type and number of skin areas affected. They are:
- paucibacillary—five or fewer lesions with no bacteria detected in the skin smear (sample taken from the area)
- multibacillary—more than five lesions or bacteria is detected in the skin smear, or both
The Ridley-Jopling system is used globally in clinical studies. It has six classifications based on severity of symptoms. They are:
- intermediate leprosy—a few flat lesions that sometimes heal by themselves and can progress to a more severe type
- tuberculoid leprosy—a few flat lesions, some large and numb; some nerve involvement; can heal on its own, persist, or may progress to a more severe form
- borderline tuberculoid leprosy—lesions like tuberculoid but small and more numerous; less nerve enlargement; may persist, revert to tuberculoid, or advance to another form
- mid-borderline leprosy—reddish plaques, moderate numbness, swollen lymph glands; may regress, persist, or progress to other forms
- borderline lepromatous leprosy—many lesions with flat lesions, raised bumps, plaques, and nodules, sometimes numb; may persist, regress, or progress
- lepromatous leprosy—many lesions with bacteria; hair loss; nerve involvement; limb weakness; disfigurement; does not regress
Leprosy is spread through contact with mucous of infected person, usually when he or she sneezes or coughs. The disease is not highly contagious. Close, frequent contact with an untreated person is required to contract leprosy.
The bacteria responsible for leprosy multiply very slowly. Therefore,the disease has an incubation period (the time between infection and the appearance of the first symptoms) of up to five years. Symptoms may not appear for as long as 20 years (WHO, 2010).
According to the New England Journal of Medicine, a certain type of armadillo native to the southern United States can also carry and transmit the disease to humans (NEJM, 2011).
The main symptoms of leprosy include:
- muscle weakness
- numbness in the hands, arms, feet, and legs
- skin lesions that:
- have decreased sensation to touch, temperature, or pain
- do not heal after several weeks or month
- are lighter than your normal skin tone
Your doctor will conduct a physical exam to look for telltale signs and symptoms of the disease.He or she will also perform a skin biopsy or scraping. Your doctor will remove a small piece of skin and send it to a laboratory for testing.
In addition, your doctor may perform a lepromin skin test to determine which form of leprosy you have.A small amount of leprosy-causing bacteria is injected into the skin, typically on the upper forearm. People who have tuberculoid or borderline tuberculoid leprosy will experience irritation at the injection site.
WHO developed a multidrug therapy in 1995 to cure all types of leprosy. It is available free of charge worldwide (WHO, 2010). Additionally, several antibiotics are used to treat leprosy by killing the bacteria that causes it, including:
Your doctor may prescribe more than one antibiotic at the same time. He or she also may want you to take an anti-inflammatory medication such as aspirin, prednisone, orthalidomide. However, never take thalidomide if you are or may become pregnant. It can produce severe birth defects.
Serious complications may occur when diagnosis and treatment are delayed. Complicationsinclude:
- hair loss, particularly on the eyebrows and eyelashes
- muscle weakness
- permanent nerve damage in the arms and legs
- inability to use the hands and feet
- chronic nasal congestion, nosebleeds, and collapse of the nasal septum
- iritis (inflammation of the iris of the eye), glaucoma (an eye disease that causes damage to the optic nerve), and blindness
- erectile dysfunction and infertility
- kidney failure
The overall outlook is good if leprosy is diagnosed promptly. Early treatment prevents tissue damage, stops the spread of the disease, and prevents serious health complications.
The outlook is worse when the disease is diagnosed at a more advanced stage, after it has caused significant disfigurementor disability. It may be impossible to lead a normal life despite treatment in these cases.
The best means of preventing leprosy is to avoid long-term, close contact with an untreated, infected person.