What's in this article?
What Is Leprosy?
Leprosy is a chronic, progressive bacterial infection caused by the bacterium Mycobacterium leprae. It primarily affects the nerves of the extremities, the lining of the nose, and the upper respiratory tract. Leprosy produces skin sores, nerve damage, and muscle weakness. If it isn’t treated, 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.
Leprosy is common in many countries, especially those with tropical or subtropical climates. However, it’s not as common in the United States. The National Institute of Allergy and Infectious Disease reports that only 100 to 200 new cases are diagnosed in the United States each year.
read more: Difference Between Leprosy and Psoriasis
What causes leprosy?
Leprosy is caused mainly by Mycobacterium leprae, a rod-shaped bacillus that is an obligate intracellular (only grows inside of certain human and animal cells) bacterium. M. leprae is termed an “acid fast” bacterium because of its chemical characteristics. When special stains are used for microscopic analysis, it stains red on a blue background due to mycolic acid content in its cell walls. The Ziehl-Neelsen stain is an example of the special staining techniques used to view the acid-fast organisms under the microscope.
Currently, the organisms cannot be cultured on artificial media. The bacteria take an extremely long time to reproduce inside of cells (about 12-14 days as compared to minutes to hours for most bacteria). The bacteria grow best at 80.9 F-86 F, so cooler areas of the body tend to develop the infection. The bacteria grow very well in the body’s macrophages (a type of immune system cell) and Schwann cells (cells that cover and protect nerve axons). M. leprae is genetically related to M. tuberculosis (the type of bacteria that cause tuberculosis) and other mycobacteria that infect humans. As with malaria, patients with leprosy produce anti-endothelial antibodies (antibodies against the lining tissues of blood vessels), but the role of these antibodies in these diseases is still under investigation.
In 2009, investigators discovered a new Mycobacterium species, M. lepromatosis, which causes diffuse disease (lepromatous leprosy). This new species (determined by genetic analysis) was found in patients located in Mexico and the Caribbean islands.
What are the symptoms of leprosy?
Leprosy primarily affects the skin and the nerves outside the brain and spinal cord, called the peripheral nerves. It may also strike the eyes and the thin tissue lining the inside of the nose.
The main symptom of leprosy is disfiguring skin sores, lumps, or bumps that do not go away after several weeks or months. The skin sores are pale-coloured.
Nerve damage can lead to:
- Loss of feeling in the arms and legs
- Muscle weakness
It takes a very long time for symptoms to appear after coming into contact with the leprosy-causing bacteria. Some people do not develop symptoms until 20 or more years later. The time between contact with the bacteria and the appearance of symptoms is called the incubation period. Leprosy’s long incubation period makes it very difficult for doctors to determine when and where a person with leprosy originally became ill.
read more: Anosmia or Loss of Smell: Risk Factors & Diagnosis
What are the Signs of Leprosy
Sign of leprosy can vary depending on the individual’s immune response to M. leprae. The WHO classification system uses clinical manifestations (the number of skin lesions and nerve involvement) as well as skin smear results to distinguish between forms of the disease. The two major WHO classifications are paucibacillary (PB) leprosy and multibacillary (MB) leprosy. However, within the WHO’s simplified classification there can be a fairly wide range of patient presentations.
- Paucibacillary leprosy
- Two to five skin lesions with negative skin smear results at all sites
- Paucibacillary single lesion leprosy
- One skin lesion with negative skin smear results
- Multibacillary leprosy
- More than five skin lesions with or without or positive skin smear results at any site
The Ridley-Jopling classification is another classification system that is used globally in evaluating patients in clinical studies and contains five different classifications of leprosy that further define the patient’s severity of symptoms and disease progression. The six different categories, in order of increasing severity of disease, include indeterminate leprosy, tuberculoid leprosy, borderline tuberculoid leprosy, mid-borderline leprosy, borderline lepromatous leprosy, and lepromatous leprosy.
In general, the signs and symptoms of leprosy may vary with the form of the disease and include the following:
- Flat or raised skin lesions or nodules, often less pigmented than the surrounding skin, though they may appear reddish or copper colored
- Single or multiple skin lesions that are often found on cooler parts of the body such as the face, buttocks, and extremities
- Thickening of the skin and peripheral nerves
- Ulcerations of the skin
- Peripheral nerve involvement leading to loss of sensation
- Peripheral nerve involvement leading to muscle weakness (for example, clawed hand deformities, contractures, and foot drop)
- Testicular involvement leading to sexual dysfunction or sterility
- Eye involvement including eye pain, eye redness, inability to close the eyelids, corneal ulcers, and blindness
- Loss of eyebrows and eyelashes
- Destruction of the nasal cartilage
read more: Bullous Pemphigoid Treatment
How Does Leprosy Spread?
Leprosy spreads through contact with the mucus of an infected person. This usually occurs when the infected person sneezes or coughs. The disease isn’t highly contagious. Close, repeated contact with an untreated person can lead to contracting leprosy.
The bacteria responsible for leprosy multiply very slowly. 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.
According to the New England Journal of Medicine, an armadillo native to the southern United States can also carry and transmit the disease to humans.
What are the risk factors for leprosy?
People at highest risk are those who live in the areas where leprosy is endemic (parts of India, China, Japan, Nepal, Egypt, and other areas) and especially those people in constant physical contact with infected people. In addition, there is some evidence that genetic defects in the immune system may cause certain people to be more likely to become infected (region q25 on chromosome 6). Additionally, people who handle certain animals that are known to carry the bacteria (for example, armadillos, African chimpanzee, sooty mangabey, and cynomolgus macaque) are at risk of getting the bacteria from the animals, especially if they do not wear gloves while handling the animals.
read more: Elephantiasis: Human Diseases and Conditions